Co-reporter:Hua Li and Yuhua Wang
Inorganic Chemistry September 5, 2017 Volume 56(Issue 17) pp:10396-10396
Publication Date(Web):August 21, 2017
DOI:10.1021/acs.inorgchem.7b01315
The paper reported the synthesis of mixed-valence Eu-doped Mg3Ca3(PO4)4 by solid-state reaction in the air atmosphere. The luminescence measurements indicated that the obtained phosphors exhibit a broad bluish-green fluorescence of Eu2+ and a sharp orange-red emission of Eu3+ excited by 395 nm. The abnormal reduction mechanism could be explained by a charge compensation model. A tunable luminescence was realized based on the reduction of Eu3+ to Eu2+ changed along with increasing the sintering time. The reduction of Eu3+ to Eu2+ in Mg3Ca3(PO4)4 host was effected by the oxygen vacancy defects when the samples sintered in different atmosphere and sintered for different lengths of time, and the oxygen vacancies which act as the electron traps were investigated with thermoluminescence. All of the results almost indicated the oxygen vacancy could weaken the reduction of Eu3+ to Eu2+. Our investigation of Mg3Ca3(PO4)4:Eu could provide a practical basis and theoretical basis to study the effect of oxygen vacancy on the emission of Eu ions.
Co-reporter:Hang Chen, Jianyan Ding, Xin Ding, Xicheng Wang, Yaxin Cao, Zhengyan Zhao, and Yuhua Wang
Inorganic Chemistry September 18, 2017 Volume 56(Issue 18) pp:10904-10904
Publication Date(Web):August 28, 2017
DOI:10.1021/acs.inorgchem.7b01021
A series of nitride solid solutions (Ca1–xSrx)16Si17N34:0.03Eu2+ were successfully synthesized through the conventional solid-state method. The electronic crystal structure and photoluminescence characteristics were studied in detail. The excitation in the near-ultraviolet and blue regions of the samples shows a broad band in the 250–550 nm range, which can match well with the n-UV and blue lighting-emitting diode chips. Partial substitution of Ca2+ by Sr2+ results in a redshift emission, and the impacts of Sr content on the luminescence were researched in detail. Under 410 nm excitation, the phosphor exhibited tunable red emission from 616 to 653 nm by changing the concentration of Sr2+. Based on the crystal data, the emission can be fitted into three distinguished Gaussian components, which are attributed to the different Eu2+ luminescence centers occupied in three disparate Ca2+ (Sr2+) lattice sites. The temperature quenching property of the phosphor was also investigated, and the good thermal stability of the phosphors was analyzed through the activation energy for thermal quenching. And the obtained CCT values from 2642 to 2817 K are suitable for a warm white light region. All the results indicated that the phosphors have possible application in the warm white light-emitting diodes.
Co-reporter:Jianyan Ding, Quansheng Wu, Yanyan Li, Qiang Long, Yichao Wang, Xinlong Ma, and Yuhua Wang
The Journal of Physical Chemistry C May 11, 2017 Volume 121(Issue 18) pp:10102-10102
Publication Date(Web):April 19, 2017
DOI:10.1021/acs.jpcc.7b01945
For solving the problem that Eu3+-activated phosphors cannot be well excited by the near UV-LED chips, the charge transfer band (CTB) of Eu3+-N3– in α-M3B2N4 (M = Ca, Sr) has been investigated in this work. Compared with the sharp excitation peaks due to the f–f transitions of Eu3+, the charge transfer band is broad and the excitation band of α-M3B2N4 (M = Ca, Sr):Eu3+ centered at 370 or 350 nm lies in near-UV, implying a promising excitation. The electron and crystal structures of α-M3B2N4 (M = Ca, Sr) has been analyzed in detailed, indicating that they all crystallize in cubic phase with the space group (Im3̅m) and have similar band-gap structures. The double bond of [N = B═N]3– combining with the face-shared (Ca, Sr)N6 octahedron forms the stable and compact crystal structure, and the band gap with the value about 4 eV is suitable for Eu3+ to form a luminescent center. Under near-UV excitation, the sharp red light that peaked at 613 and 593 nm resulting from the f–f transition of Eu3+ ions has been obtained. The optimal concentration of Eu3+ in the α-M3B2N4 (M = Ca, Sr) has been measured, and the decay curves of samples prove that the energy transfer happens between Eu3+ ions through the dipole–dipole interaction. The thermal stability of samples has been measured to access their application in the WLED.
Co-reporter:Xin Ding and Yuhua Wang
ACS Applied Materials & Interfaces July 19, 2017 Volume 9(Issue 28) pp:23983-23983
Publication Date(Web):June 27, 2017
DOI:10.1021/acsami.7b06612
In this work, we synthesized a new Eu2+-doped oxide-matrix-based LiBa12(BO3)7F4 broad red emission phosphor. It can emit red light peaking at ∼644 nm under NUV excitation with the coordinate at (0.6350, 0.3586) and a sensitive color gamut for eyes. This phosphor with a special kind of tunnel crystal structure and layered distribution of Ba2+ is contributed to longer wavelength emission. By theoretical calculation and analysis using local state density energy band structure simulation of Eu2+ doped in different site, the origin of the observed emission center was distinguished. Furthermore, decay curves analysis also indicated there are three possible Ba2+ sites for Eu2+ to occupy. Temperature-dependent PL spectra appeared anomalous phenomena that the intensity increases first and then decreases, which is due to the traps energy level’s contribution of electron’s transition. The phosphor also has cathodoluminescence (CL) property which the spectra take on typical current saturation phenomenon. The CL curves indicated that this phosphor has a very good stability under much electron beam bombardment time. After fabricated combining with BAM, (Sr, Ba)2SiO4 and our red phosphor excited under 405-nm NUV chips, warm light LED was obtained. Its CIE coordinate is (0.3475, 0.3416) and the CCT, Ra, and luminous efficiency are 4856 K, 84.1, and 72.6 lm/W, respectively.Keywords: LED; luminescence; oxide; red light; structure;
Co-reporter:Yichao Wang, Jianyan Ding, and Yuhua Wang
The Journal of Physical Chemistry C December 7, 2017 Volume 121(Issue 48) pp:27018-27018
Publication Date(Web):November 15, 2017
DOI:10.1021/acs.jpcc.7b09783
A series of novel garnet structure phosphors Ca2-xY1+xZr2-xAl3+xO12:yCe3+(0 ≤ x ≤ 0.4) (0 ≤ y ≤ 0.07) were synthesized by the solid state reaction and developed by the Ca2YZr2Al3O12–YAG solid solution design. Structure information on the phosphors all were refined using the Rietveld method based on the XRD date, they all show the general cubic garnet structure with the space group Ia3̅ d, the variation of the cell parameter and the average bond lengths is investigated, which is match well with the theoretical calculation. The band structure of the phosphors have been calculated using the density function theory method, the band gaps gradually become narrow with the increase of x, demonstrated by the diffuse reflectance spectra. The photoluminescence properties were investigated on aspects of the emission and excitation spectra, quantum efficiency, thermal stability and the decay curves. The possible mechanisms and reasons for the photoluminescence properties variations have been discussed in detail. All the phosphor can be efficiently excited by the near-ultraviolet chips, according to the double-substitution for Ca2+/Zr4+ by Y3+/Al3+, the emission light can be changed from cyan to green, with the peak shifting from 496 to 514 nm. The internal quantum efficiency all exceed 50%. An excellent WLED lamp was obtained by fabricating our Ca1.6Y1.4Zr1.6Al3.4O12:0.03Ce3+ phosphor with BAM:Eu2+, (Sr, Ca)AlSiN3:Eu2+ and 395 nm GaN chip, its CIE coordinate (x, y), CCT, and Ra are (0.3603, 0.348), 4404 K, and 87. These results reveal the correlations between structure and properties for phosphors and provide a practical basis to engineer and develop novel phosphors for the n-UV LEDs.
Co-reporter:Tianrong Li, Yongliang Shao, Shouting Zhang, Jingcan Qin, Long Fan, Li Liu, Baodui Wang, Zhengyin Yang, Yuhua Wang
Journal of Luminescence 2017 Volume 181() pp:345-351
Publication Date(Web):January 2017
DOI:10.1016/j.jlumin.2016.09.036
In order to obtain high selectivity and high quenching efficiency fluorescent sensors for 2,4,6-trinitrophenol (TNP), a ligand [5-(diethylamino)-2-((quinolin-8-ylimino)methyl)phenol hydrochloride, H2LCl] was obtained by the condensation of 4-(diethylamino)salicylaldehyde and 8-aminoquinoline in the present of HCl; and two Zn(II) complexes, namely [Zn2(μ2-L)(μ2-CH3COO)2Cl] (1) and [Zn2(μ2-L)2(NO3)2] (2), were also prepared via the reaction of H2LCl with Zn(AcO)2·2H2O or Zn(NO3)2·6H2O. 1 (in chloroform) and 2 (in methanol) showed strong emission centered at 498 nm and 540 nm respectively, and both of them displayed superior selectivity and high quenching efficiency to TNP among other nitroaromatics and analogues (i.e., 2,4,6-trinitrotoluene, phenol, nitrobenzene, o-nitrophenol, p-nitrotoluene, m-nitrotoluene, and salicylic acid). 6 equ. of TNP made 92% fluorescence quenching of 1, and 8 equ. of TNP induced 85% quenching of 2. The detection limits for TNP were found to be 0.154 ppm of 1 and 1.01 ppm of 2.
Co-reporter:Linna Guo, Xiong Zheng, Sheng Zhang, Benliang Zhao, Yuhua Wang
Materials Research Bulletin 2017 Volume 86() pp:1-4
Publication Date(Web):February 2017
DOI:10.1016/j.materresbull.2016.09.011
•The discovery of a novel phosphor Lu6O5F8:Yb3+/Ho3+/Li+ will be of great value.•Upconversion and Cathodoluminescence emission properties are studied and compared.•Reasons for the new experimental phenomenon are discussed.Yb3+/Ho3+/Li+ tridoped Lu6O5F8 as a novel phosphor was prepared by a coprecipitation method. It is found that Li+ doping could enhance the emission intensity of Yb3+/Ho3+ codoped Lu6O5F8 both under the excitation at 980 nm and low-voltage electron beam. Under 980 nm laser excitation, the intensity of red emission is slightly stronger than that of green emission, generating an overall yellow output in Lu6O5F8:20%Yb3+,1%Ho3+,x%Li+ (0 ≤ x ≤ 8) nanoparticles, and the reason for this phenomenon is discussed in detail. Meanwhile, under low-voltage electron beam excitation, spectral results demonstrated that the intensity of red emission is much stronger than that of green emission, yielding a red color output. Therefore, Lu6O5F8:20%Yb3+,1%Ho3+,x%Li+ (0 ≤ x ≤ 8) nanoparticles have potential applications in luminescent display panels and field emission displays.
Co-reporter:Tianrong Li, Yang Yang, Panpan Zhou, Zhou Peng, Jingcan Qin, Li Liu, Yuhua Wang
Polyhedron 2017 Volume 128(Volume 128) pp:
Publication Date(Web):28 May 2017
DOI:10.1016/j.poly.2017.03.014
In order to achieve an effective “turn-on” fluorescence detection of Cu2+, a rhodamine 6G-based sensor [1-phenyl-3-methyl-5-hydroxypyrazole-4-benzoyl(rhodamine 6G) hydrazone, 1] was prepared. Fluorescence and UV–Vis absorption titration, detection limit, single crystal structure, binding mode, and quantum mechanical calculation studies were also discussed in detail. Sensor 1 showed highly selectivity and sensitivity to Cu2+ among common cations (Na+, K+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Zn2+, Cd2+, Cr3+, Fe3+ and Cu2+) in acetonitrile. Upon addition of Cu2+, a new absorption band at 523 nm, and a strong emission band centering at 557 nm appeared in 1 solution. Relevant solution changed from colorless to purple, and an obvious orange fluorescence emission was given. A maximum fluorescence enhancement of 250 times at 557 nm could be made by addition of 6 equivalent of Cu2+. The fluorescence detection limit was calculated to be 2.5 μM (0.20 ppm) for Cu2+, and 1:1 stoichiometry between Cu2+ and 1 was proved. In the single crystal of 1–Cu2+ complex, rhodamine moiety exhibited an open cycle form. We believe 1 can be a good candidate for the fluorescence detection of Cu2+.Sensor 1, 1-phenyl-3-methyl-5-hydroxypyrazole-4-benzoyl(rhodamine 6G) hydrazone, showed a “turn-on” fluorescence response to Cu2+ among common cations (Na+, K+, Mg2+, Ca2+, Mn2+, Co2+, Ni2+, Zn2+, Cd2+, Cr3+, Fe3+ and Cu2+) selectively and sensitively. The single crystals of 1–Cu2+ complex definitely support the corollary that after chelating with Cu2+, an open cycle structure is formed in rhodamine moiety.Download high-res image (71KB)Download full-size image
Co-reporter:Yichao Wang, Jianyan Ding, Yanyan Li, Xin Ding, Yuhua Wang
Chemical Engineering Journal 2017 Volume 315(Volume 315) pp:
Publication Date(Web):1 May 2017
DOI:10.1016/j.cej.2017.01.044
•A series of novel phosphors Ba3Y1−yLuyAl2O7.5: Ce3+ was successfully synthesized.•The Ba3Y1−yLuyAl2O7.5 consist of Y(Lu)O6 and AlO4 layers with three lattice sites.•The phosphors show good absorption ranging from ultraviolet to blue region.•The emission light can be modulated in a large range of blue-green colors.•The mechanisms of the changes for luminescence property are studied in detail.A series of novel blue-green broadband emitting phosphors Ba3Y1−yLuyAl2O7.5: Ce3+ (0 ⩽ y ⩽ 0.5) were synthesized via the solid state reaction. The crystal structure and the photoluminescence properties were investigated for the application in white light-emitting diodes. The phosphors have two Ba2+ sites and one Y(Lu)3+ site with different coordination environment. These phosphors show the good absorption ranging from the ultraviolet to the blue region, the emission spectra contain both blue and green compositions, and the peaks can shift from 478 nm to 493 nm by changing the doped Lu3+ concentration, the mechanisms and reasons of the changes of the PL/PLE spectra, fluorescence decay curves and thermal quenching properties have also been studied in detail. The critical distance for Ce3+ ions in the Ba3YAl2O7.5 host was calculated to be 23.85 Å and the energy transfer mechanism occurs among the nearest-neighbor ions. The above results indicate that Ba3Y1−yLuyAl2O7.5: Ce3+ is a good candidate as the blue-green component for near-UV LEDs.
Co-reporter:Yuanjie Yang, Yuhua Wang, Shu Yin
Applied Surface Science 2017 Volume 420(Volume 420) pp:
Publication Date(Web):31 October 2017
DOI:10.1016/j.apsusc.2017.05.176
•SnO2 nanoparticles with homogeneous oxygen vacancies were synthesized via a simple hydrothermal method.•The homogeneous oxygen vacancies led to desirable electronic structure.•The unique electronic structure induced remarkable visible light photocatalytic activity.Electronic structure in principle determines the light absorbance, charge transfer and separation, and consequently, photocatalytic property of a photocatalyst. Herein, we report rutile SnO2 with a desirable electronic structure that exhibits a narrowed bandgap and an increased valence band width resulted from the introduction of homogeneous oxygen vacancies. XPS, Raman, ESR and PL spectra demonstrate the homogeneous oxygen vacancies confined in SnO2 nanoparticles. Moreover, the first principle calculations theoretically reveal the desirable electronic structure. The narrowed bandgap further contributes to extended light absorption range and the increased valence band width leads to efficient charge transfer and separation, hence facilitating the visible light photoreactivity. As a result, the defected SnO2 exhibits a superior visible light photocatalytic activity. More strikingly, the photodegration of methyl orange (MO) is completely accomplished within only 20 min under λ ≥ 420 nm. Briefly, this work both experimentally and theoretically indicates that homogeneous oxygen vacancies confined in SnO2 nanoparticles lead to the optimized electronic structure and, consequently, the remarkable visible light photocatalytic activity. This could open up an innovative strategy for designing potentially efficient photocatalysts.Download high-res image (163KB)Download full-size image
Co-reporter:Tongyao Liu, Bin Liu, Linfen Yang, Xinlong Ma, Hao Li, Shu Yin, Tsugio Sato, Tohru Sekino, Yuhua Wang
Applied Catalysis B: Environmental 2017 Volume 204(Volume 204) pp:
Publication Date(Web):5 May 2017
DOI:10.1016/j.apcatb.2016.12.011
•Novel RGO/Ag2S/TiO2 UV-NIR response heterostructure photocatalysts have been synthesized successfully.•Strong absorption of UV-NIR light improves the sunlight utilization effectively and the degradation rate of organic pollutants.•The synergetic effects of RGO, Ag2S and TiO2 enhance the photocatalytic activity and stability.A series of novel RGO/Ag2S/TiO2 heterostructure photocatalysts has been synthesized successfully by a facial hydrothermal and simple ionexchange method. During the preparation, the reduction of graphene oxide (GO) and growth of TiO2 and Ag2S are accomplished smoothly, and the functions of each part are developed well together. Compared with pure TiO2, Ag2S and Ag2S/TiO2 nanocomposite, the obtained 3 wt.% RGO/Ag2S/TiO2 nanocomposite exhibits a significant enhancement of ultraviolet (UV) and near-infrared (NIR) light photocatalytic activities. Owing to its extended photoresponsive range, great adsorptive property and efficient electron-hole separation capacity. Furthermore, benefited by the introduction of reduced graphite oxide (RGO), the deterioration of Ag2S is inhibited well and the stability of RGO/Ag2S/TiO2 nanocomposite has been enhanced greatly.Download high-res image (252KB)Download full-size image
Co-reporter:Xinlong Ma, Hao Li, Tongyao Liu, Shanshan Du, Qinping Qiang, Yuhua Wang, Shu Yin, Tsugio Sato
Applied Catalysis B: Environmental 2017 Volume 201(Volume 201) pp:
Publication Date(Web):1 February 2017
DOI:10.1016/j.apcatb.2016.08.029
•The phenomenon of photocatalytic reaction-induced selective corrosion of ZnO nanosheets was firstly revealed.•The impacts of this special corrosion and photocorrosion on morphology and photocatalytic stability were compared.•The special corrosion-induced active face loss turns out to be fatal for the photocatalytic stability.•A direct and visual confirmation of inhibitory effect of loaded Ag against selective corrosion is revealed.In previous work, the photocatalytic stability during the recycled degradation is employed to evaluate the inhibitory effect of photocorrosion. Then, a significant question arises: is the photocatalytic stability only related to the photocorrosion for zinc oxide (ZnO)? The answer turns out to be no in our work. The phenomenon of photocatalytic reaction-induced selective corrosion of ZnO nanosheets was firstly revealed. It is found that the special corrosion not only needs ultraviolet (UV) light irradiation, but also results from the photocatalytic reaction. Then, the impacts of this special corrosion and photocorrosion on morphology and photocatalytic stability were compared. It is found that the photocatalytic reaction-induced selective corrosion shows more mass loss, more selective etching and more decrease of unit mass photocatalytic activity than that of photocorrosion. The results indicate that the special corrosion-induced active face loss rather than the photocorrosion-induced mass loss can be fatal for the photocatalytic stability. Accordingly, a direct and visual confirmation of inhibitory effect of loaded Ag against selective corrosion is revealed.Download high-res image (242KB)Download full-size image
Co-reporter:Tongyao Liu, Xinlong Ma, Linfen Yang, Hao Li, Huihui Li, Soo Wohn Lee, Yuhua Wang
Applied Catalysis B: Environmental 2017 Volume 217(Volume 217) pp:
Publication Date(Web):15 November 2017
DOI:10.1016/j.apcatb.2017.05.080
•CaSn(OH)6/SnO2 heterostructures have been synthesized via a one-pot hydrothermal process through tuning ratios of materials.•Doping of Fe3+ in 0.8CSH substrate effectively adjusts band structure and increases the separation efficiency of charge carriers.•Increased photocatalytic activities are achieved by tuning CaSn(OH)6/SnO2 interaction and optimizing Fe3+ concentration.A series of novel CaSn(OH)6/SnO2 heterostructure (CSH) photocatalysts have been synthesized via a facile one-pot hydrothermal process with different molar ratios of raw materials. The obtained CaSn(OH)6/SnO2 composite with CaCl2:SnCl4 = 0.8 (0.8CSH) exhibits outstanding ultraviolet (UV)-light photocatalytic activity, which could be attributed to the efficient separation of photogenerated electrons and holes. Meanwhile, the doping of Fe3+ ions into 0.8CSH substrate greatly enhances the UV and visible-light photocatalytic activities, and the photodegradation rate of 1.0 mol% Fe-doped CSH (1.0FCSH) sample exceeds that of 0.8CSH by a factor of more than 14 times. This could be attributed to the fact that Fe-doping induces the shift of the absorption edge into the visible light region and reduces the recombination of electron-hole pairs. Overall, this research can provide an effective approach to synthesize new efficient photocatalysts and facilitate their application in environmental protection.Download high-res image (339KB)Download full-size image
Co-reporter:Shaoze Yu, Dan Wang, Chunfang Wu, Yuhua Wang
Materials Research Bulletin 2017 Volume 93(Volume 93) pp:
Publication Date(Web):1 September 2017
DOI:10.1016/j.materresbull.2017.03.044
•Use facile and mild precipitation method obtained Sr2P2O7:Eu2+/Eu2+,Mn2+ phosphors.•Through controlling the morphology to tune the photoluminescence properties.•The columnar structure Sr2P2O7:Eu2+ phosphor shows better emission intensity.•Self-assembled phenomenon appears by changing the Mn2+ concentration of the Sr2P2O7:Eu2+,Mn2+ phosphor.Sr2P2O7:Eu2+/Eu2+,Mn2+ phosphors have been synthesized by the facile and mild precipitation method and they are characterized by X-ray powder diffraction, scanning electron microscopy, photoluminescence spectra. The SEM results indicate the obtained Sr2P2O7:Eu2+ phosphors have the columnar structure and the Sr2P2O7:Eu2+,Mn2+ phosphors is the sphere like. The effects of the stirring and sintering temperature on the morphology of Sr2P2O7:Eu2+/Eu2+,Mn2+ phosphors have been investigated. The photoluminescence spectra of Sr2P2O7:Eu2+ and Sr2P2O7:Eu2+,Mn2+ phosphors showed that the Sr2P2O7:Eu2+ phosphors can be excited by 345 nm and exhibit blue emission around 421 nm and the Sr2P2O7:Eu2+,Mn2+ phosphors can be excited by 355 nm and exhibited the emission around 420 nm and 578 nm showing the white light.
Co-reporter:Jiejun Ren;Xuan Dong;Gangyi Zhang;Tianrong Li
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 22) pp:13961-13967
Publication Date(Web):2017/11/06
DOI:10.1039/C7NJ03017G
All-inorganic perovskite quantum dots (PeQDs) have attracted much attention recently owing to their excellent illumination properties; however, the instability of PeQDs has restricted their application. In this work, we successfully synthesized CsPbX3 (X = Br, I) PeQD/Ergo films by encapsulation of PeQDs within Ergo® optical adhesive 8500 (Ergo 8500). The CsPbX3 PeQD/Ergo films exhibited great water-resistance and air-stability. The photoluminescence of the films was stable for weeks in water and months in air. By trying different structures and PeQDs volumes, CsPbX3 PeQD/Ergo white LEDs (W-LEDs) were successfully fabricated. The CsPbX3 PeQD/Ergo W-LEDs exhibited high quality white light with a CIE color coordinate of (0.3692, 0.3442) and correlated color temperature of 4059 K.
Co-reporter:Gen Li
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 17) pp:9178-9183
Publication Date(Web):2017/08/21
DOI:10.1039/C7NJ01890H
Novel phosphors BaGd2Si3O10:RE2+/3+ (RE = Eu or Ce) were designed and prepared by a solid state reaction. The crystal structure was characterized by X-ray diffraction. The optical band gap was estimated by the diffuse reflectance spectrum. The photoluminescence properties were investigated and the results indicate that under ultraviolet light excitation, BaGd2Si3O10:Eu3+, BaGd2Si3O10:Eu2+ and BaGd2Si3O10:Ce3+ phosphors show red, green and blue emission, respectively. The trichromatic emission available by doping different rare earth ions proves that BaGd2Si3O10 should be a promising host material for phosphors in white LEDs.
Co-reporter:Gen Li;Yu Fan;Haijie Guo
New Journal of Chemistry (1998-Present) 2017 vol. 41(Issue 13) pp:5565-5571
Publication Date(Web):2017/06/26
DOI:10.1039/C7NJ01171G
Novel Ce3+-doped SrSc2O4 phosphors were synthesized via a solid state method. The crystal structure and morphology were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The photoluminescence properties, quantum efficiency, CIE value and thermal stability of SrSc2O4:Ce3+ phosphors were investigated in detail to evaluate their application in LEDs. The photoluminescence results revealed that the phosphors have an excitation band in the blue region from 400 to 470 nm and a broad green emission band peaking at about 491 nm. The above results indicated that the phosphors can be effectively excited by blue light and could be promising candidates as green-emitting phosphors for application in LEDs.
Co-reporter:Hao Li;Yue Jing;Xinlong Ma;Tongyao Liu;Linfeng Yang;Bin Liu;Shu Yin;Yongzhi Wei
RSC Advances (2011-Present) 2017 vol. 7(Issue 14) pp:8688-8693
Publication Date(Web):2017/01/23
DOI:10.1039/C6RA26498K
In order to overcome the intrinsic drawback of pristine g-C3N4, we demonstrate a simple thermal oxidation exfoliation-photodeposition technique to fabricate a Ag/graphene-like g-C3N4 (Ag/G-g-C3N4) photocatalyst. It was revealed that the monodispersed Ag nanoparticles were well dispersed on the surface of graphene-like g-C3N4 (G-g-C3N4). The Ag/G-g-C3N4 displayed an enhanced photocatalytic activity for methylene blue degradation and the degradation rate was 10 times higher than that of pristine g-C3N4 under visible light irradiation. The enhancement of photocatalytic activity could be attributed to the surface plasmon resonance effect of Ag and large surface area (189.9 m2 g−1) of G-g-C3N4, which improve the visible light absorption ability and provide abundant reactive sites as well as promoting photogenerated electron–hole pair separation.
Co-reporter:Aijun Mao;Zhengyan Zhao
RSC Advances (2011-Present) 2017 vol. 7(Issue 68) pp:42634-42640
Publication Date(Web):2017/09/04
DOI:10.1039/C7RA07085C
Oxynitride Li2SrSiON2 was synthesized by introducing N3− into the Li2SrSiO4 lattice, which is suitable for Eu2+ doping. It crystallizes in an trigonal structure with the space group of P3121 (152) and cell parameter a = b = 5.0131(0) Å, c = 12.4270(1) Å and V = 270.46 Å3. Under blue light (450 nm) excitation, the representative sample Li2Sr0.98SiON2:0.02Eu2+ exhibits a bright broad band orange emission peaking at 586 nm with an external quantum efficiency of 52.7%. Its emission intensity at 150 °C remained 78% of that measured at 25 °C. Warm white light-emitting diode 1 (W-LED1) was prepared by combining a blue LED chip and LSSON:0.02Eu2+. High color rendering index (Ra ∼ 90) warm W-LED2 was fabricated by combing a blue light chip, BaSi2O2N2:Eu2+, and Li2Sr0.98SiON2:0.02Eu2+. The chromaticity coordinate and correlated color temperature (CCT) of W-LED2 are (0.3625, 0.3539) and ∼4386 K, respectively. Excellent optical properties allow it to be an attractive orange phosphor for warm W-LEDs.
Co-reporter:Haijie Guo;Gen Li;Jie Liu;Peng Feng;Dongwei Liu
Journal of Materials Chemistry C 2017 vol. 5(Issue 11) pp:2844-2851
Publication Date(Web):2017/03/16
DOI:10.1039/C7TC00133A
We developed a novel long-lasting phosphorescence (LLP) material BaZrSi3O9:Eu2+,Pr3+. The crystal structure, electronic structure and photoluminescence of this phosphor have been investigated systematically. The highlight of this work is the admirable LLP performances of BaZrSi3O9:Eu2+,Pr3+, which could be observed by the naked eye for 15 hours in the dark after ceasing the irradiation source. Moreover, we have analyzed the reason why the BaZrSi3O9:Eu2+,Pr3+ phosphor has such excellent persistent luminescence by exploring the distribution of traps in BaZrSi3O9:Eu2+,Pr3+ with the help of thermoluminescence (TL) spectra. A series of the excitation duration, decay duration and temperature dependent TL experiments of BaZrSi3O9:Eu2+,Pr3+ were conducted, revealing the trapping and detrapping of electrons into and from the shallow traps through the conduction band and the deeper traps via the tunnelling process. According to the experimental results, the mechanism of the feasible persistent luminescence of BaZrSi3O9:Eu2+,Pr3+ was also proposed and illustrated in detail.
Co-reporter:Wanying Geng;Xufeng Zhou;Jianyan Ding;Gen Li
Journal of Materials Chemistry C 2017 vol. 5(Issue 44) pp:11605-11613
Publication Date(Web):2017/11/16
DOI:10.1039/C7TC02561K
In this work, a novel potassium-calcium silicate-fluoride based phosphor: K7Ca9[Si2O7]4F (KCSOF) has been successfully synthesized by a solid-state reaction at low temperature. The occupation of Ce3+ is studied by Rietveld refinement, luminescence properties and decay curves. KCSOF:Ce3+ presents a wide absorption band ranging from 240 to 420 nm and displays blue emission (λmax = 445 nm). Good thermal stability has also been detected, which shows that it still retains 90% of the initial intensity at 200 °C. In addition, a white LED device has been manufactured by connecting a 380 nm UV chip with a blend of KCSOF:Ce3+, (Sr, Ba)SiO4:Eu2+ and CaAlSiN3:Eu2+. The color coordinates, correlated color temperature and color rendering index of the manufactured LED device are (0.421, 0.407), 3256 K and 95.55, respectively. These results suggest that the blue-emitting KCSOF:Ce3+ phosphor has good prospects for applications in white UV LEDs.
Co-reporter:Haijie Guo;Gen Li;Jie Liu;Peng Feng;Dongwei Liu
Journal of Materials Chemistry C 2017 vol. 5(Issue 46) pp:12090-12096
Publication Date(Web):2017/11/30
DOI:10.1039/C7TC03579A
A barizite-like compound BaHfSi3O9 (BHS) was tailored to emit intense bluish green persistent luminescence (PersL) above the recognizable intensity level (≥0.32 mcd m−2) lasting for more than 12 h through codoping with Eu2+ and Pr3+. X-ray powder diffraction, the crystal and electronic structures, photoluminescence (PL) and photoluminescence excitation (PLE) were basically studied. Furthermore, decay curves, as well as thermo-luminescence (TL) spectra, were systematically carried out to clarify the mechanism of the PersL. We used the excitation duration, decay duration and excitation temperature dependent TL experiments to estimate the trap density distribution in BHS:Eu2+,Pr3+ phosphor. Based on the above measurements, the positive defects could be responsible for the bluish green PersL at room temperature. In the process of PersL, the electrons captured by shallow traps transfer to the Eu2+ levels through a conduction band (CB) which leads to a rapid decay in the early decay stage (t < 3 h), whereas the electrons trapped by deep traps through a quantum tunnelling process result in much slower and nonexponential decay behavior in the later slow-decay stage (t > 3 h). A possible mechanism is proposed for the PersL process in BHS:Eu2+,Pr3+ phosphor.
Co-reporter:Xin Ding
Physical Chemistry Chemical Physics 2017 vol. 19(Issue 3) pp:2449-2458
Publication Date(Web):2017/01/18
DOI:10.1039/C6CP08300E
A novel apatite mineral of Ba5(PO4)2SiO4 was synthesized successfully using a traditional high temperature solid-state reaction. Its structure was determined by high-resolution transmission electron microscopy, fast Fourier transform, energy dispersive X-ray spectroscopy, and X-ray powder diffraction Rietveld refinement, and this was found to be a hexagonal crystal system with the space group attributed to P63/m (176). Moreover, a series of Eu2+ doped Ba5(PO4)2SiO4 phosphors were investigated. The photoluminescence (PL) properties of Ba5(PO4)2SiO4:Eu2+ were investigated in detail by density functional theory calculations, diffuse reflection spectra, emission–excitation spectra, decay curves, and temperature dependence spectra. It can emit green light peaking at ∼515 nm under 405 nm NUV excitation with quantum efficiency 31.89%. According to structure and photoluminescence (PL) property analysis, Eu2+ can occupy two kinds of Ba2+ site. The concentration quenching mechanism of Eu2+ could be a d–d interaction luminescence center. It has poor temperature stability properties because of too much temperature-dependent electron–phonon interaction at high temperature. Fabricated white-LEDs using a 405 nm GaN NUV chip combined with a blend of RGB phosphors: CaAlSiN3:Eu2+, Ba5(PO4)2SiO4:1%Eu2+ and BAM:Eu2+, driven by 30 mA current can get warm-white light with chromaticity coordinates (0.355, 0.342) and correlated color temperature (CCT) 4561 K. This demonstrates that Ba5(PO4)2SiO4:Eu2+ is a potential green phosphor matching NUV LED chips to get white light.
Co-reporter:Yaxin Cao;Jianyan Ding;Xin Ding;Xicheng Wang
Journal of Materials Chemistry C 2017 vol. 5(Issue 5) pp:1184-1194
Publication Date(Web):2017/02/02
DOI:10.1039/C6TC04827G
Novel single-phase phosphors with the multi-cation-site Na2BaCa(PO4)2:Eu,xMn were synthesized by a traditional solid-state reaction method. The photoluminescence (PL) investigation indicated that the emitting light was tunable from blue to yellow with a variation in the Mn content and reaches a warm white with the CIE coordinate of (0.36, 0.32) and corresponding color temperature (CCT) of 4346 K when x is 0.07. The framework of the NBCP was compact, and the Ca2+ polyhedron is coplanar with the Ba2+ polyhedron one by one along the c axis, sharing 6 O2− ions on the edge. This is the reason for the excellent thermally stability of the phosphors, which keep more than 90% of the initial PL intensity under 150 °C. Based on these facts, NBCP:Eu,xMn has potential application as a white light emitting diode (WLED). Cathodoluminescence (CL) properties were also investigated, and the phosphor has considerable luminescence intensity and high current saturation intensity.
Co-reporter:Gen Li, Yuhua Wang, Haijie Guo, Jie Liu, Dongwei Liu, Peng Feng
Journal of Luminescence 2017 Volume 192(Volume 192) pp:
Publication Date(Web):1 December 2017
DOI:10.1016/j.jlumin.2017.06.037
Novel long lasting phosphorescence materials BaSc2Si3O10:Eu2+, RE3+ (RE3+ = Nd3+, Tm3+, Dy3+ and Tb3+) are designed and prepared by a solid state reaction. According to the density functional theory calculations, the conduction band is mostly composed of Sc 3d states, and Ba states have almost no contribution to the conduction band. Their photoluminescence emission spectra show a broad asymmetric blue emitting band peaking at about 443 nm, attributed to the 5d-4f transitions of Eu2+ ion occupying Ba and Sc site respectively. According to the analysis on electronic structure and optical properties of the phosphors, it is believed that due to the special form of conduction band and the occupying situation of emission center, only the Eu2+ ion occupying the Sc site is involved in the long lasting phosphorescence process, resulting in the interesting phenomenon that the blue emitting phosphors show green phosphorescence. Additionally, the experimental results show that co-doping the trivalent rare earth ions, especially Nd3+ or Dy3+ ions, can improve the long lasting phosphorescence performance effectively in BaSc2Si3O10:Eu2+ system. This work shows up an interesting phosphorescence phenomenon, and provides a direct experimental evidence that conduction band plays an important role in the long lasting phosphorescence process.
Co-reporter:Shanshan Du, Deyin Wang, Qinping Qiang, Xinlong Ma, Zuobin Tang and Yuhua Wang
Journal of Materials Chemistry A 2016 vol. 4(Issue 29) pp:7148-7155
Publication Date(Web):05 Jul 2016
DOI:10.1039/C6TC01812B
Micro-sized Gd6O5F8 particles doped with Yb3+, Ho3+ and Li+ ions have been synthesized by a facile hydrothermal route. The dual-model up- and down-conversion luminescence was investigated under visible blue (VIS-B) light (451 nm) and near infrared (NIR) light (980 nm) excitations. The structural properties of the products are analysed by X-ray diffraction (XRD). Upon excitation to the 2F5/2 level of Yb3+ using a 980 nm laser diode, Gd6O5F8:Yb3+,Ho3+ exhibits intense up-converted green and red emission at 545 nm and 660 nm, which correspond to the 5S2 → 5I8 and 5F5 → 5I8 transitions of Ho3+, respectively. The nearly quadratic dependence of the green/red emission intensity on the excitation power indicates that a two-photon up-conversion process was involved to populate the green (5S2) and red levels (5F5) of Ho3+. In contrast, upon excitation Ho3+ to its 5F1 level by 451 nm blue light, both visible and near-infrared emissions peaking at 545 nm, 660 nm, 980 nm and 1191 nm are simultaneously observed in the emission spectra, which are assigned to the 5S2 → 5I8 (Ho3+), 5F5 → 5I8 (Ho3+), 2F5/2 → 2F7/2 (Yb3+) and 5I6 → 5I8 (Ho3+) transitions, respectively. Meanwhile, the emission intensities of the up-converted green emission and down-converted emissions were further enhanced by co-doping Li+, which can be confirmed by the fact that the emission intensities of the up-converted green emission and down-converted NIR emission were increased 50% and 90% after co-doping 7% Li+. The energy transfer processes between Ho3+ and Yb3+ ions and the mechanisms of Li+ doping for the emission enhancement have been investigated and discussed. Additionally, the time-resolved luminescence traces are measured, and the luminescence lifetimes of the Ho3+ ions are calculated. Furthermore, the temperature-dependent up-conversion and down-shifted luminescence of Gd6O5F8:Yb3+,Ho3+,Li+ are investigated, and the results show that the ratio of up-converted green to red emission as well as the ratio of down-shifted green to blue emission in Gd6O5F8:Yb3+,Ho3+,Li+ all respond single exponentially to temperature, which could be applied to sense temperature.
Co-reporter:Gen Li, Yuhua Wang, Wei Zeng, Wenbo Chen, Shaochun Han, Haijie Guo and Yanyan Li
Journal of Materials Chemistry A 2016 vol. 4(Issue 15) pp:3304-3312
Publication Date(Web):10 Mar 2016
DOI:10.1039/C5TC04396D
A series of novel Ce3+ singly doped and Ce3+/Tb3+ codoped color-tunable NaBaScSi2O7 phosphors were synthesized via the solid state method. The morphology, UV-vis reflectance, photoluminescence emission and excitation spectra, the lifetime and the thermal quenching properties were investigated in detail. NaBaScSi2O7:Ce3+ phosphors showed intense blue emission at about 425 nm, corresponding to the transitions from the lowest 5d excited state to the 2F5/2 and 2F7/2 spin orbit 4f ground states of Ce3+ ions, under optimal excitation of 349 nm. Under excitation of Ce3+ ions at 349 nm, the emission spectra of NaBaScSi2O7:Ce3+,Tb3+ phosphors consisted of a blue emission band of Ce3+ ions at 425 nm and a series of strong green emission lines at 488, 542, 582, and 625 nm due to the 5D4 → 7FJ (J = 6, 5, 4, and 3) characteristic transitions of Tb3+ ions. A possible energy transfer mechanism was proposed and ascribed to the dipole–dipole interaction on the basis of the experimental results and analysis. In addition, the cathodoluminescence properties of NaBaScSi2O7:Ce3+,Tb3+ were also studied in detail. The current results indicate that NaBaScSi2O7:Ce3+,Tb3+ can serve as a potential phosphor for application in UV-WLEDs and FEDs.
Co-reporter:Zuobin Tang, Deyin Wang, Waheed U. Khan, Shanshan Du, Xicheng Wang and Yuhua Wang
Journal of Materials Chemistry A 2016 vol. 4(Issue 23) pp:5307-5313
Publication Date(Web):29 Apr 2016
DOI:10.1039/C6TC01449F
A novel blue-emitting zirconium silicate phosphor K2ZrSi2O7:Eu2+ was prepared by solid-state reaction for the first time, and its crystal structure was determined from the XRD profiles by using Rietveld refinement and high-resolution transmission electron microscopy (HRTEM). The photoluminescence properties were investigated for the possible application in white light-emitting diodes (LEDs). The excitation spectra of the Eu2+ doped K2ZrSi2O7 phosphor show broad band excitation in the 250–410 nm region, and upon excitation at 350 nm, this phosphor showed a strong blue emission centered at 462 nm (full-width at half-maximum (FWHM) ∼ 70 nm). The thermal stability can be enhanced significantly by solid solution. The cathodoluminescence properties of K2ZrSi2O7:Eu2+ were also studied. Under continuous low-voltage electron bombardment, the phosphors display excellent degradation resistance and good color stability. A white LED fabricated with this phosphor and yellow-orange emitting phosphor Sr3SiO5:Eu2+ on a LED chip (λmax = 375 nm) was discussed. Driven by a 350 mA forward bias current, the fabricated lamp gives intense white light with a higher color rendering index of 86. All the results indicate that this phosphor has potential application in LEDs and FEDs.
Co-reporter:Xin Ding, Ge Zhu, Wanying Geng, Qian Wang, and Yuhua Wang
Inorganic Chemistry 2016 Volume 55(Issue 1) pp:154-162
Publication Date(Web):December 15, 2015
DOI:10.1021/acs.inorgchem.5b02048
A series of novel red emission Mg3Ga2GeO8 (MGG):Mn4+ phosphors under near-UV (NUV) excitation are synthesized successfully by traditional high-temperature solid-state reaction. The structure of Mg3Ga2GeO8 is investigated by high-resolution transmission electron microscopy, scanning electron microscopy, and powder X-ray diffraction (XRD) Rietveld refinement. It has one octahedral site and one tetrahedral site in the crystal structure. According to XRD and photoluminescence (PL) property analysis, Mn4+ can occupy an octahedral (Mg2+/Ga3+) site. The PL properties are investigated by diffuse-reflectance, emission, excitation, and temperature-dependent spectroscopy and decay curves. It can emit red light peaking at 659 nm under NUV excitation. The critical quenching concentration of Mn4+ was about 0.5 mol %. The concentration quenching mechanism could be a d–d interaction for the Mn4+ center. The CIE chromaticity coordinates and full-width at half-maximum are (0.295, 0.677) and 24 nm, respectively. It demonstrated that MGG:Mn4+ has high color purity. The PL intensity of MGG:0.5% Mn4+ drops to 72% when the temperature is raised up to 150 °C. Furthermore, MGG:0.5% Mn4+ exhibits outstanding quantum efficiency (64.7%). By tuning of the weight ratio of blue, green, and red phosphors, the fabricated white-light-emitting diodes using a 405 nm GaN NUV chip combined with a blend of blue phosphor BAM:Eu2+, green phosphor Sr2SiO4:Eu2+, and red-emitting phosphor MGG:Mn4+ driven by 40 mA current can get white light with chromaticity coordinates (0.316, 0.375) and CCT = 3340 K. This demonstrates that MGG:Mn4+ is a potential red phosphor matching NUV LED chips to get white light.
Co-reporter:Xicheng Wang, Zhengyan Zhao, Quansheng Wu, Yanyan Li, and Yuhua Wang
Inorganic Chemistry 2016 Volume 55(Issue 21) pp:11072
Publication Date(Web):October 12, 2016
DOI:10.1021/acs.inorgchem.6b01711
A series of Ca2YZr2Al3O12:Eu3+ (CYZA) phosphors were successfully synthesized through conventional solid-state method. The electronic structure and their photoluminescence or cathodoluminescence properties were investigated in detail. Under n-UV excitation, the CYZA:Eu3+ exhibits more intense red emission than the commercial Y2O3:Eu3+ phosphor. A WLED lamp with good color render index was obtained by fabricating the phosphor with BAM:Eu2+ and LuAG:Ce3+ phosphors. The phosphor also exhibits red emission with high current saturation and high resistance under low voltage electron bombardment. The degradation resistance can be compared to the commercial Y2O3:Eu3+ phosphor. All the results indicate that the CYZA:Eu3+ has potential applications in both white LEDs and FEDs.
Co-reporter:Jianyan Ding, Quansheng Wu, Yanyan Li, Qiang Long, Yichao Wang, Xinlong Ma, and Yuhua Wang
Inorganic Chemistry 2016 Volume 55(Issue 21) pp:10990
Publication Date(Web):October 25, 2016
DOI:10.1021/acs.inorgchem.6b01480
Defect luminescence has been considered to be one of the most efficient ways to resolve the problem of the recent limited supply and increased demand for rare-earth elements. So, in this work, a novel self-activated long-persistent green-yellow and yellow emitting phosphors of α-Ca3B2N4 and β-Ca3B2N4 has been successfully synthesized by sample-pressuring sintering. The α-Ca3B2N4 and β-Ca3B2N4 all have a broad excitation band peaked at 300 and 350 nm and emit yellow-green light peaked at 550 nm and yellow light peaked at 575 nm respectively with the long afterglow properties. The crystal structures and electron structures of α-Ca3B2N4 and β-Ca3B2N4 have been investigated to show that orthorhombic β-Ca3B2N4 corresponds to an ordered superstructure of cubic α-Ca3B2N4 and the phase transformation between α-Ca3B2N4 and β-Ca3B2N4 would happen during the preparation process, which produces many intrinsic defects forming the luminescent center. The thermoluminescence (TL) curve shows that there are traps in the host lattice with the TL peak located at 310 K. The results indicate that α-Ca3B2N4 and β-Ca3B2N4 with the defect-related PL and LPL properties have potential applications in the LED and LPL used phosphors.
Co-reporter:Xin Ding, Qian Wang and Yuhua Wang
Physical Chemistry Chemical Physics 2016 vol. 18(Issue 11) pp:8088-8097
Publication Date(Web):16 Feb 2016
DOI:10.1039/C6CP00168H
A series of novel K2Ge4O9:Mn4+ phosphors with red emission under blue light excitation have been synthesized successfully by traditional high-temperature solid-state reaction. The structure of K2Ge4O9 has been investigated by high-resolution transmission electron microscopy, scanning electron microscopy and X-ray powder diffraction with Rietveld refinement. The PL properties have been investigated by measuring diffuse reflection spectra, emission spectra, excitation spectra, decay curves and temperature-dependent spectra. The KGO:0.1% Mn4+ phosphor can emit red light peaking at 663 nm under UV or blue light excitation. The critical quenching concentration of Mn4+ was about 0.1 mol%. The concentration quenching mechanism could be a d–d interaction for the Mn4+ center. The CIE chromaticity coordinates and FWHM are (0.702, 0.296) and 20 nm, which demonstrated that the K2Ge4O9:Mn4+ has a high color purity. By tuning the weight ratio of yellow and red phosphors, the fabricated white LEDs, using a 455 nm InGaN blue chip combined with a blend of the yellow phosphor YAG:Ce3+ and the red-emitting KGO:Mn4+ phosphor driven by a 40 mA current, can get white light with chromaticity coordinates (0.405, 0.356) and CCT 3119 K. These results indicated that K2Ge4O9:Mn4+ is a potential red phosphor to match blue LED chips to get warm white light.
Co-reporter:Shanshan Du, Deyin Wang and Yuhua Wang
CrystEngComm 2016 vol. 18(Issue 5) pp:728-735
Publication Date(Web):21 Dec 2015
DOI:10.1039/C5CE02129D
This paper reports on a facile hydrothermal route that has been developed to synthesize a precursor Gd(OH)2.14F0.86 and a novel phosphor host Gd6O5F8. The morphology of the micro-sized Gd(OH)2.14F0.86/Gd6O5F8 can be easily tuned in a controlled manner by altering the fluorine sources, alkali solutions, reaction time and the pH values of the initial solution. Under ultraviolet (UV) light, vacuum ultraviolet (VUV) light and low-voltage electron beam excitation, the Gd(OH)2.14F0.86/Gd6O5F8:Ln3+ (Eu, Tb and Tm) samples show the characteristic f–f transitions of the Ln3+ ions and give bright red, green and blue emissions, respectively. The results prove that the as-synthesized Gd6O5F8 are excellent host lattices for rare earth luminescence, which may find potential applications in solid-state light, field emission displays (FEDs).
Co-reporter:Wenbo Chen, Yuhua Wang, Wei Zeng, Shaochun Han, Gen Li, Haijie Guo, Yanyan Li and Qinping Qiang
New Journal of Chemistry 2016 vol. 40(Issue 1) pp:485-491
Publication Date(Web):04 Nov 2015
DOI:10.1039/C5NJ02438B
Enhancing the afterglow intensity and prolonging the persistence time, stimulates the applications of long persistent phosphors. However, current methods to improve the luminescent properties of persistent phosphors are invariably complicated. In this work, we demonstrate a simple but effective strategy to manipulate and expand the color of persistent luminescence, through the radiative energy transfer from CaAl2O4:Eu2+,Nd3+ (CA) to Y3Al5O12:Ce3+ (YAG). It is significant to observe that in the CA/YAG composites, the afterglow intensity can be enhanced ∼2.7-fold and the persistence time can be prolonged ∼2.8-fold in comparison with the widely used CA. A white light persistent luminescent composite (B:Y = 10:5) with a decay time of 45 h is obtained. Investigations into the mechanism indicate that the great enhancement of the intensity and persistence time of the long persistent luminescence is directly driven by photopic luminous efficiency and the photo-releasing of energy stored in deep traps. Moreover, the persistent luminescence color of the composites can be tuned from blue to yellow through adjusting the YAG content. In addition, the potential and universality of this color manipulation approach are validated. These results will be greatly beneficial for the applications of long persistent phosphors.
Co-reporter:Qiang Long, Chuang Wang, Yanyan Li, Jianyan Ding, Yuhua Wang
Journal of Alloys and Compounds 2016 Volume 671() pp:372-380
Publication Date(Web):25 June 2016
DOI:10.1016/j.jallcom.2016.01.249
•An novel green emitting phosphor was firstly synthesized by solid state reaction.•The excitation spectra match well with n-UV chips and the quantum efficiency is 67.4%.•The thermal stability of the phosphor is superior to commercial phosphors.An Eu2+-activated Sr8ZnLu(PO4)7 (SZLP:Eu2+) green emitting phosphor was synthesized and its crystal structure has been refined and determined from the XRD profiles by Rietveld refinement method. The excitation spectra of the SZLP:Eu2+ phosphors covered the range from 250 to 450 nm, which matches well with n-UV chips. SZLP:Eu2+ exhibited broad-band green emission centered at about 520 nm under 400 nm irradiation with a high quantum efficiency (QE) value of 67.4% and good thermal stability, its emission intensity remains 77% at 150 °C of that measured at room temperature. In addition, to investigate its application in field emission displays, the cathodoluminescence spectra of SZLP:Eu2+ as a function of the accelerating voltage, probe current and the electron radiation time were also measured and discussed in detail. Excellent degradation resistance properties with good color stability were obtained by continuous low-voltage electron-beam excitation of the phosphor.
Co-reporter:Si Chen, Jiangtao Chen, Jianlin Liu, Jing Qi, Yuhua Wang
Applied Surface Science 2016 Volume 387() pp:103-108
Publication Date(Web):30 November 2016
DOI:10.1016/j.apsusc.2016.06.085
Highlights
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We obtained ZnO nanowire arrays grown on ZnO seed layer on Si with MgO buffer.
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FE properties of ZnO nanowire arrays grown on ZnO seed layer on Si with MgO buffer is better than that without MgO buffer.
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With MgO buffer, the ZnO seed layer shows lower top-bottom resistance and better electron transport.
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The enhanced field emission properties can be attributed to good electron transport in seed layer, good nanowire alignment because of MgO buffer.
Co-reporter:Haijie Guo, Yuhua Wang, Wenbo Chen, Wei Zeng, Gen Li and Yanyan Li
New Journal of Chemistry 2016 vol. 40(Issue 1) pp:613-618
Publication Date(Web):13 Nov 2015
DOI:10.1039/C5NJ02575C
A yellow emitting long-lasting phosphor based on a Ca6BaP4O17 matrix was successfully synthesized by means of solid state method in a reducing atmosphere. The persistent phosphor was characterized in detail by X-ray powder diffraction (XRD), photoluminescence (PL), persistent luminescence and decay curves as well as thermoluminescence (TL) spectra. When irradiated by ultraviolet light in advance, Ca6BaP4O17:0.02Eu2+,0.015Gd3+ phosphor shows a yellow persistent luminescence dominating at ∼553 nm at room temperature due to the 5d–4f transitions of Eu2+ ions and the chromaticity coordinate was calculated to be (0.431, 0.545), which is in the yellow region. Moreover, investigation of TL curves reveals that the incorporation of Gd3+ ion creates more appropriate energy traps and increases the density of intrinsic traps leading to the enhancement of afterglow. Consequently, the initial long lasting phosphorescence (LLP) intensity of Ca6BaP4O17:0.02Eu2+,0.015Gd3+ (0.21 cd m−2) is significantly enhanced by a factor of 2 compared with Ca6BaP4O17:0.02Eu2+,0.015Ho3+ and the sustained phosphorescence also can last approximately 19 h above the recognizable intensity level (0.32 mcd m−2). In order to study the trapping process and explain the mechanism of long afterglow, a schematic model is also proposed and discussed in detail.
Co-reporter:Gen Li, Yuhua Wang, Dongwei Liu, Haijie Guo and Jie Liu
RSC Advances 2016 vol. 6(Issue 62) pp:57024-57032
Publication Date(Web):08 Jun 2016
DOI:10.1039/C6RA11515B
Novel long lasting phosphorescence materials Ba2Gd2Si4O13:Eu2+, RE3+ (RE3+ = Dy3+, Ho3+, Tm3+, Nd3+ and Tb3+) are designed and prepared by a solid state reaction. Their photoluminescence emission spectra show a broad asymmetric green emitting band peaking at 517 nm, attributed to the 5d–4f transitions of Eu2+ ion occupying Ba2+ and Gd3+ site respectively. The Eu2+ ion occupying the Gd3+ site is not involved in the long lasting phosphorescence process, resulting in an interesting phenomenon that the green emitting phosphors show cyan phosphorescence. The experimental results show that co-doping the rare earth ions can improve the long lasting phosphorescence performance effectively, and with the moderate introduction of Nd3+ ion the most persistent cyan emission can last for 3 h approximately. This work shows up an interesting phosphorescence phenomenon, and provides a new and efficient candidate for long lasting phosphorescence materials.
Co-reporter:Wenbo Chen, Yuhua Wang, Wei Zeng, Gen Li and Haijie Guo
RSC Advances 2016 vol. 6(Issue 54) pp:48411-48414
Publication Date(Web):11 May 2016
DOI:10.1039/C6RA07994F
Novel yellow emitting persistent phosphors β-Ba3P4O13:Eu2+ and β-Ba3P4O13:Eu2+,Ga3+ were successfully synthesized via solid-reaction method. Ga3+ was proved to be an effective codopant to enhance persistent luminescence in Eu2+-doped β-Ba3P4O13 phosphors. Eu2+–Ga3+ codoped β-Ba3P4O13 showed about 6 times longer persistence time than the Eu2+-singly-doped phosphors. The yellow long persistent luminescence (LPL) of β-Ba3P4O13:Eu2+,Ga3+ can persist about 10 h. The thermoluminescence (TL) analyses showed that co-doping Ga3+ can improve more appropriate traps leading to the enhancement of the afterglow. These results suggested that Ga3+ may play a critical role in creating traps in β-Ba3P4O13:Eu2+.
Co-reporter:Jianyan Ding, Yanyan Li, Quansheng Wu, Qiang Long, Yichao Wang and Yuhua Wang
RSC Advances 2016 vol. 6(Issue 11) pp:8605-8611
Publication Date(Web):13 Jan 2016
DOI:10.1039/C5RA25831F
In this work, a novel self-activated light emitting phosphor of Na2TiSiO5 (NTSO) has been successfully synthesized in a high temperature solid-state reaction. The photoluminescence (PL) and cathodoluminescence (CL) properties of NTSO have been measured. Under excitation at 260 nm, NTSO emits a white light with CIE chromaticity coordinates (0.275, 0.355) and cyan light can also be observed at low voltage excitation. The crystal structure of NTSO has been investigated using the Rietveld refinement, which shows that Ti ions not only occupy the octahedron center but also connect with five O ions to form a TiO5 polyhedron. The special polyhedron of TiO5 broadens the emission band, and the energy transfer between the two sites has also been proved through the time-resolved photoluminescence (TRPL) spectra. Finally, the CL properties of NTSO with the functions of accelerating voltage, filament current and electron radiation time have been measured and the results show that NTSO emits bright light, and has excellent stability and good CIE chromaticity coordinates, which indicates that NTSO has the potential to be applied in FEDs.
Co-reporter:Wenbo Chen, Yuhua Wang, Wei Zeng, Gen Li and Haijie Guo
RSC Advances 2016 vol. 6(Issue 1) pp:331-337
Publication Date(Web):16 Dec 2015
DOI:10.1039/C5RA19762G
Near-infrared (NIR) persistent phosphors have many remarkable optical advantages in bioimaging applications. However, only a very few activators and hosts have been found to exhibit NIR persistent luminescence. Here, we report Eu2+-activated phosphate NIR long persistent phosphors, Ca4(PO4)2O:Eu2+,R3+ (R = Lu, La, Gd, Ce, Tm, Y). All the codoped samples showed persistent luminescence peaking at a long wavelength of ca. 690 nm due to the 5d–4f transitions of Eu2+. The persistent luminescence of Ca3.97(PO4)2O:Eu0.012+,Y0.023+ can be detected for 2 h after the removal of excitation. As a key parameter of persistent phosphors, the trap depths can be tuned from 0.62 to 0.77 eV by codoping with trivalent rare earth ions. The I−1–t curves reveal that two effective traps contribute to long persistent luminescence of Y3+, Tm3+ and Ce3+ codoped samples, whereas there is only one effective trap for La3+, Gd3+ and Lu3+ codoped samples, which was confirmed by the thermoluminescence curves of the codoped samples. This investigation provided a new long persistent phosphor which enriches the activator and hosts of existing NIR long persistent phosphors for potential application in vivo bioimaging.
Co-reporter:Wenjin Xu, Xin Ding and Yuhua Wang
New Journal of Chemistry 2016 vol. 40(Issue 5) pp:4735-4743
Publication Date(Web):17 Mar 2016
DOI:10.1039/C5NJ02991K
To explore a new phosphor, Ca9La(GeO4)0.75(PO4)6 was investigated to obtain better understanding of its synthesis and crystal structure. Ce3+/Tb3+ co-doped Ca9La(GeO4)0.75(PO4)6 green phosphor was successfully synthesized with the objective of application in ultraviolet-based light-emitting diodes. The characteristic photoluminescence properties were analysed by photoluminescence excitation (PLE) spectra, emission (PL) spectra and decay times. Ca9La(GeO4)0.75(PO4)6 offers high thermal stability in the green-emission area. Instead of thermal quenching, with the increase in temperature, the intensity of Tb3+ increases slightly. To explain this special phenomenon reasonably, an implicit mechanism between thermal quenching and energy transfer is proposed based on the configurational coordinate diagram. This mechanism could be a helpful reference for understanding the thermal properties of multiple activator Ce3+ and Tb3+ co-doped phosphors.
Co-reporter:Seyede Sara Khalili and Hossein Dehghani
RSC Advances 2016 vol. 6(Issue 13) pp:10880-10886
Publication Date(Web):26 Jan 2016
DOI:10.1039/C5RA24053K
Copper sulfide (CuS) is one of the most important counter electrodes (CEs) in high-efficiency, quantum dot-sensitized solar cells (QDSSCs). In this work, we investigated the effect of Mg, Ca, Sr and Ba ion incorporation into the CuS layer on the photovoltaic performance of quantum dot-sensitized solar cells. Metal ion-doped CuS was deposited by the successive ionic layer adsorption and reaction (SILAR) method on the FTO substrate. As a result, the quantum dot photoanode with the optimized Ca-doped CuS CE exhibited power conversion efficiency (PCE) of 2.33%, which is much higher than bare CuS CE (PCE 1.68%), Ba-doped CuS (1.81%), Mg-doped CuS (1.82%) and Sr-doped CuS (1.67%). A sandwiched structural Ca-doped CuS/graphen sheet (Ca-doped CuS/GS) electrode was prepared by repeating electrophoretic deposition (EPD) of graphene sheets and deposition of Ca-doped CuS nanoparticles. When a Ca-doped CuS/graphene sheet (Ca-doped CuS/GS) was used as a CE, the QDSSC exhibited higher power conversion efficiency (2.73%) compared to cells with Ca-doped CuS (2.33%) and bare-CuS (1.68%) cathodes. A full description of reasons for efficiency enhancement are discussed in this paper by using diverse electrochemical and spectral analyses.
Co-reporter:Gen Li, Yuhua Wang, Wei Zeng, Wenbo Chen, Shaochun Han, Haijie Guo, Jie Liu
Materials Research Bulletin 2016 Volume 84() pp:1-6
Publication Date(Web):December 2016
DOI:10.1016/j.materresbull.2016.07.020
•The optically stimulated luminescence property of NaBaScSi2O7:Eu2+ was studied.•The introduction of Nd3+ ion enhances the LLP and OSL properties of NaBaScSi2O7:Eu2+.•The persistent green emission can last for about five and a half hours.•A possible mechanism for the optical phenomenon is proposed.Green emitting NaBaScSi2O7:Eu2+/Eu2+, Nd3+ phosphors are prepared by a solid state reaction under a reductive atmosphere. The introduction of Nd3+ ion, which acts as trap center, largely extends the thermoluminescence characteristics and evidently enhances the long lasting phosphorescence and optically stimulated luminescence properties of the phosphors. The persistent green emission of the co-doped phosphor can last for about five and a half hours above recognizable intensity level (≥0.32 mcd/m2). According to the analysis of thermoluminescence characteristics, it is concluded that the shallow T1′ traps with a continuous trap depth distribution are exactly the traps that lead to the long lasting phosphorescence and other three kinds of deep traps, i.e., T2′, T3′ and T4′, corresponding to a separated trap depth distribution, should mainly contribute to the optically stimulated luminescence performance. Finally, a possible mechanism for the optical phenomenon is proposed.
Co-reporter:Quansheng Wu, Jianyan Ding, Xicheng Wang, Yanyan Li, Yuhua Wang
Materials Research Bulletin 2016 Volume 83() pp:649-656
Publication Date(Web):November 2016
DOI:10.1016/j.materresbull.2016.07.018
Owe to the increase of crystallinity with Al3+ incorporating, the photoluminescent intensity of the phosphors increased by 49%.The modified structure results in a strong covalence of Eu-N and improved the thermal quenching behavior.The stronger covalent coordination environment for Eu2+ lead to a red-shift of the emission.Cation substitution is a useful method to modify the structure and luminescence properties of nitridosilicate phosphors. The crystal structure of pure nitride Ca-α-sialon with the composition Ca1.3+0.5xAl2.8+xSi9.2⿿xN16:Eu0.1 is changed by cation substitution (Al3+ ⿿ Si4+). Smooth changes of lattice parameters with x indicate that Al3+ ions have been effectively incorporated into the Ca1.4Al2.8Si9.2N16 lattice. Although the replacement of Si4+ by Al3+ expands the lattice volume, the covalent coordination environment for Eu2+ becomes stronger. Eventually, the emission exhibits a red-shift. Owing to the increase of the crystallinity with Al3+ introducing, the emission intensity of the phosphors increases by 49%. The modified structure results in a strong covalence of Eu-N and an improvement of the thermal quenching.
Co-reporter:Zuobin Tang, Deyin Wang, Yuhua Wang, Waheed U. Khan, Shanshan Du
Materials Research Bulletin 2016 Volume 83() pp:336-339
Publication Date(Web):November 2016
DOI:10.1016/j.materresbull.2016.06.020
BaZrSi3O9:Bi3+ has a broad absorption band in 300⿿400 nm and gives bright yellow emission.BaZrSi3O9:Bi3+ exhibits a good thermal stability with increasing heating temperature.BaZrSi3O9:Bi3+ shows excitation-dependent emission.A yellow-emitting phosphor, BaZrSi3O9:Bi3+, was synthesized in air via solid state reaction method. Luminescence properties of this phosphor were examined by steady-state and time-resolved as well as temperature-dependent luminescence spectra. The obtained BaZrSi3O9:Bi3+ sample shows strong absorption in 300⿿400 nm, and gives bright and broad yellow emission centered at 560 nm upon 350 nm excitation. The broad emission is originated from 3P1 ⿿ 1S0 transition of Bi3+, which has a lifetime around ⿼1 μs in BaZrSi3O9. Upon heating in the temperature range from room temperature to 250 °C, accompanied by the emission intensity deceases (emission intensity at 150 °C retains 76% its initial intensity at room temperature), the emission of Bi3+ in BaZrSi3O9 is blue-shifted, which is ascribed to the thermally active phonon-assisted tunneling from the lower energy to the higher energy emission band in the excited states of Bi3+.
Co-reporter:Yanyan Li, Wenbo Chen, Yuhua Wang
Materials Research Bulletin 2016 Volume 84() pp:363-369
Publication Date(Web):December 2016
DOI:10.1016/j.materresbull.2016.08.029
•A novel yellow phosphor high-Ba3P4O13:Eu2+ was synthesized.•High-Ba3P4O13:Eu2+ shows an extreme broad band with FWHM of 175 nm.•The phosphor shows nearly no absorption in the blue region.•The white light can be obtained by blending the phosphor and BAM:Eu2+.We have synthesized and investigated a series of yellow-emitting high-Ba3P4O13:Eu2+ phosphors, showing an extreme broad band at around 587 nm, with a full width at half maximum of about 175 nm, which is attributed to the 5d-4f transition of Eu2+ under near ultraviolet excitation. This phosphor shows good absorption in the near ultraviolet range and nearly no absorption in the blue region. The concentration quenching and the fluorescence lifetime of Eu2+, as well as the temperature-dependent photoluminescence have also been studied. Moreover, a white light with chromaticity coordinates of (0.364, 0.357) and color temperature of 4354 K was obtained by blending the yellow-emitting high-Ba3P4O13:Eu2+ and the commercial blue-emitting BaMgAl10O17:Eu2+ phosphor. These results indicate that high-Ba3P4O13:Eu2+ has potential applications in the dual-color-phosphor-converted white light-emitting diodes.
Co-reporter:Xin Ding, Ge Zhu, Wanying Geng, Masayoshi Mikami and Yuhua Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 26) pp:6676-6685
Publication Date(Web):21 May 2015
DOI:10.1039/C5TC01123J
The structural properties of wadeite (K2ZrSi3O9) have been investigated using high-resolution transmission electron microscopy and X-ray powder diffraction refinement, and the luminescence properties of Eu2+ activated K2ZrSi3O9 have been studied to explore new material for phosphor-converted white light near-ultraviolet light-emitting diodes (NUV-LEDs). Eu2+ was introduced into the K2ZrSi3O9 host in a reducing atmosphere, and the special crystallographic positions of Eu2+ were determined based on XRD, photoluminescence emission spectra, temperature dependence properties, and time-resolved photoluminescence. The calculated band gap is about 4.7 eV. The CIE chromaticity coordinates and FWHM of the blue phosphor K2ZrSi3O9:1%Eu2+ are (0.1538, 0.1857) and 57 nm respectively. The photoluminescence properties of co-doped Eu2+–Al3+and Eu2+–Sc3+ charge compensation pair phosphors were investigated. The Eu2+ single-doped K2ZrSi3O9 phosphor shows blue emission with a broad band peaking at 465 nm upon 400 nm NUV excitation. With Eu2+–Al3+ as the charge compensation pair, the photoluminescence properties do not change distinctly, while the photoluminescence emission spectrum red shifts by about 39 nm and the emission becomes green with the Eu2+–Sc3+ pair. Different occupation locations of the different charge compensation pairs were discussed. Blue and green emissions can be obtained from K2ZrSi3O9:Eu2+ compounds by different charge compensation mechanisms. This reveals that K2ZrSi3O9:Eu2+ possesses remarkable optical properties and can be used in NUV-LEDs.
Co-reporter:Haijie Guo, Wenbo Chen, Wei Zeng, Gen Li, Yuhua Wang, Yanyan Li, Yang Li and Xin Ding
Journal of Materials Chemistry A 2015 vol. 3(Issue 22) pp:5844-5850
Publication Date(Web):01 May 2015
DOI:10.1039/C5TC00810G
A novel yellow-emitting long-lasting phosphate phosphor Ca6BaP4O17:Eu2+,Ho3+ is developed. The incorporation of Ho3+ ions, which act as trap centers, largely extends the thermoluminescence characteristics and evidently enhances the persistent luminescence behavior of the phosphor. Both the fluorescence and phosphorescence spectra of Ca6BaP4O17:0.02Eu2+,0.015Ho3+ reveal only one asymmetric broad emission band located at 553 nm, ascribed to the 5d–4f transitions of Eu2+ ions in two different Ca2+ sites. After 15 min of excitation, the initial long-lasting phosphorescence (LLP) intensity of Ca6BaP4O17:0.02Eu2+,0.015Ho3+ can reach about 0.13 cd m−2 and its LLP can last more than 47 h above the recognizable intensity level (0.32 mcd m−2), a phenomenon that is infrequent and excellent. Furthermore, the direct bandgap of about 4.081 eV for Ca6BaP4O17 provides a suitable bandgap for Eu2+ and Ho3+ ions. The results indicate that the phosphor has the potential to become a novel commercial LLP phosphor used in the field of emergency lighting and display. Detailed processes and a possible mechanism are studied and discussed.
Co-reporter:Xufeng Zhou, Zhiya Zhang and Yuhua Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 15) pp:3676-3683
Publication Date(Web):17 Feb 2015
DOI:10.1039/C4TC02807D
A new silicate phosphor MgGd4Si3O13:Ce3+,Tb3+ was successfully synthesized with the objective of application in ultraviolet-excited light emitting diodes (LEDs) and field emission displays (FEDs). The structural and photoluminescence (PL) properties of un-doped MgGd4Si3O13 were studied. The PL properties and the energy transfer from Gd3+ to Tb3+ and Ce3+ to Tb3+ in Ce3+ and Tb3+ singly- and co-doped MgGd4Si3O13 were discussed. Ce3+ occupying two different crystalline sites show diverse PL properties and distinct energy transfer efficiencies to Tb3+. The cathodoluminescence (CL) spectra, depending on the accelerating voltage and probe current, were also studied. Excellent degradation resistance properties with good colour stability were obtained with continuous low-voltage electron-beam excitation.
Co-reporter:Haijie Guo, Yuhua Wang, Wenbo Chen, Wei Zeng, Shaochun Han, Gen Li and Yanyan Li
Journal of Materials Chemistry A 2015 vol. 3(Issue 42) pp:11212-11218
Publication Date(Web):28 Sep 2015
DOI:10.1039/C5TC02283E
Thermoluminescence (TL) glow curves of Ca6BaP4O17:Eu2+,R3+ (R = Dy, Tb, Ce, Gd, Nd) samples were measured above room temperature in order to compare the trap distributions in the band gap. The observed phenomenon indicates that R3+ ions (R = Dy, Tb, Ce, Gd, Nd) have different effects on the trap properties of the Ca6BaP4O17:Eu2+ phosphor. The most shallow trap (0.620 eV) for the Tb3+ ion and the deepest trap (0.762 eV) for the Dy3+ ion eventually led to shorter duration (4.3 h and 1.2 h, respectively), while the appropriate trap depth (0.716 eV) for the Nd3+ ion makes the Ca6BaP4O17:Eu2+,Nd3+ sample show the longest afterglow duration (37.9 h). Codoping the Tb3+ ion slightly increases the instinct traps of the Ca6BaP4O17:Eu2+ sample and creates a new low-temperature TL peak corresponding to a relatively shallow trap leading to the strongest initial afterglow brightness (0.887 cd m−2), while codoping with other R3+ ions (R = Dy, Ce, Gd, Nd) creates new appropriate or inappropriate traps. By recording a series of long-lasting phosphorescence (LLP) spectra with various irradiated times and TL experiments with varying delay time after ceasing the UV irradiation, the trap distribution of the depth and shape was evaluated. The result provides a better understanding of the role of these trapping centers played in the persistent luminescence mechanism.
Co-reporter:Yanyan Li, Jianyan Ding, Quansheng Wu, Qiang Long, Xicheng Wang and Yuhua Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 34) pp:8949-8955
Publication Date(Web):29 Jul 2015
DOI:10.1039/C5TC01276G
A near-ultraviolet (near-UV) excited phosphor, Ca15Si20O10N30:Ce3+, was synthesized by a solid state reaction, and its crystal structure and luminescence properties were investigated in detail. Ca15Si20O10N30 crystallizes in a cubic unit cell with the space group Pa and the lattice parameters are determined to be a = b = c = 15.4195(3) Å. The maximum emission wavelength can be tuned from about 470 to 520 nm as the content of Ce3+ increases due to the energy transfer between various Ce3+ activators located in different coordination environments, which was verified by the time-resolved emission spectroscopy (TRES) and the variation in the decay rate with respect to the detection wavelength. Upon excitation at 365 nm, Ca15Si20O10N30:Ce3+ exhibited a relatively low thermal quenching, and the T50 is measured to be 233 °C. The above results indicate that Ca15Si20O10N30:Ce3+ is a promising candidate for application in white light-emitting diodes (LEDs).
Co-reporter:Jianyan Ding, Yanyan Li, Quansheng Wu, Qiang Long, Chuang Wang and Yuhua Wang
Journal of Materials Chemistry A 2015 vol. 3(Issue 33) pp:8542-8549
Publication Date(Web):14 Jul 2015
DOI:10.1039/C5TC01508A
In this work, a broad excitation band of Li2SiN2:Eu3+ with the peak at 357 nm has been found and investigated. The photoluminescence, morphologies and thermal stability of the samples were also measured. Under excitation at 357 nm and 300 nm, sharp red and green light can be observed due to the 5D0–7F2 transition of the Eu3+ ions and the 5D4–7F5 transition of the Tb3+ ions, respectively. According to the Diffuse reflectance spectra in combination with the energy level diagram of Li2SiN2:0.02Eu3+, we deduced that the broad excitation bands belong to the charge transfer band (CTB), which have also been observed in Li2SiN2:Tb3+ with the peak at 271 nm. And the thermal stabilities of the samples have been found to be connected with the CTB.
Co-reporter:Gen Li, Yuhua Wang, Wei Zeng, Wenbo Chen, Shaochun Han, Haijie Guo and Xicheng Wang
Dalton Transactions 2015 vol. 44(Issue 40) pp:17572-17578
Publication Date(Web):10 Sep 2015
DOI:10.1039/C5DT02748A
A novel green afterglow phosphor NaBaScSi2O7:Eu2+ was prepared by a solid state reaction under a reductive atmosphere. The NaBaScSi2O7:Eu2+ phosphor shows two emission bands centered at about 424 (weak) and 502 nm (strong) due to the substitution of Eu2+ in both Ba+ and Na2+ sites, and energy transfer from EuBa (424 nm) to EuNa (502 nm) was found. Both EuBa and EuNa contribute to the afterglow process while EuNa dominates. Na0.99BaScSi2O7:0.01Eu2+ exhibits green long lasting phosphorescence, whose duration is more than 1 h. The thermoluminescence properties of NaBaScSi2O7:Eu2+ and the relationship between thermoluminescence and thermal quenching properties were discussed in detail. This work provides a new and efficient candidate for long lasting phosphorescence materials.
Co-reporter:Qiang Long, Chuang Wang, Jianyan Ding, Yanyan Li, Quansheng Wu and Yuhua Wang
Dalton Transactions 2015 vol. 44(Issue 32) pp:14507-14513
Publication Date(Web):10 Jul 2015
DOI:10.1039/C5DT02368H
A near-UV excited phosphor, LiSr4(BN2)3:Eu2+ (LSBN:Eu2+), was synthesized using a solid-state reaction at 800 °C. The crystal structure of LSBN had been refined and determined from the XRD profiles by the Rietveld refinement method, which belongs to the space group Imm with the lattice constants a = b = c = 7.46112(23) Å. The excitation spectra of the LSBN:Eu2+ phosphors were centered at around 370 nm and covered the range from 300 to 450 nm. Under 400 nm excitation, the emission spectra of the LSBN:Eu2+ phosphors show a red emission centered at about 640 nm (FWHM ≈ 130 nm). And the energy transfer between the Eu2+ ions is confirmed to arise from the electric dipole–dipole interactions. The nontypical emission blue-shift in the single luminescence center with increasing temperature luminescence properties is also investigated. The results indicate that LSBN:Eu2+ could be conducive to the development of white light emitting diodes.
Co-reporter:Yang Li, Wenjing Liu, Xicheng Wang, Ge Zhu, Chuang Wang and Yuhua Wang
Dalton Transactions 2015 vol. 44(Issue 29) pp:13196-13203
Publication Date(Web):11 Jun 2015
DOI:10.1039/C5DT01409C
A double substitution induced blue-emitting phosphor Ca(Mg0.8, Al0.2)(Si1.8, Al0.2)O6:Eu2+ (CMAS:Eu2+) was successfully synthesized by a solid-state reaction process, and its structure and luminescence properties were investigated in detail. The crystal structure and chemical composition of the CMAS matrix were analyzed and determined based on Rietveld refinements and Energy Dispersive Spectroscopy (EDS). The composition-optimized CMAS:Eu2+ exhibited a strong blue light, centered at 446 nm upon excitation at 365 nm with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.144, 0.113). Under 380 nm excitation, the PL emission intensity area of the optimized phosphor was found to be 46.95% of that of the commercial BaMgAl10O17:Eu2+ (BAM:Eu2+) phosphor and the quantum efficiency of the phosphor is 41.32%. The temperature-dependent PL studies have been investigated which show the thermal stability of the CMAS:Eu2+ phosphor compared with that of the CaMgSi2O6:Eu2+ (CMS:Eu2+) phosphor.
Co-reporter:Xin Ding, Ge Zhu, Wanying Geng, Qian Wang and Yuhua Wang
CrystEngComm 2015 vol. 17(Issue 17) pp:3235-3242
Publication Date(Web):09 Feb 2015
DOI:10.1039/C5CE00020C
In this paper, we have synthesized a new garnet structure compound Ca3Hf2SiAl2O12 and a series of Ce3+-doped Ca3Hf2SiAl2O12: xCe3+ phosphors. The crystal structure and luminescence properties of the Ca3Hf2SiAl2O12: xCe3+ are investigated in detail. Transmission electron microscopy analysis and XRD Rietveld refinement shows that Ca3Hf2SiAl2O12 is body-centered cubic and belongs to Iad (230) space-group with a = 12.3666 Å. Ca3Hf2SiAl2O12: xCe3+ has broad excitation bands at 330 and 400 nm attributed to the characteristic Ce3+ 5d–4f transition and can produce cyan emission under 400 nm UV light excitation. The emission intensity of CHSA: 1%Ce3+ phosphor can reach 68.9% of YAG: Ce3+ (commercial) and 72.1% of Ca8Mg(SiO4)4Cl2: Eu2+ (commercial). The average decay lifetime of Ca3Hf2SiAl2O12: 1%Ce3+ is 48.91 ns, which is consistent with the nanosecond peculiarity of Ce3+. In the process of increasing the temperature from 25 °C to 250 °C, the integrated emission intensity of Ca3Hf2SiAl2O12: 0.5%Ce3+ only decreases to 57.8% (250 °C) and shows nice thermal stability compared with commercial YAG: Ce3+(P46-Y3). Furthermore, Ca3Hf2SiAl2O12: 0.5%Ce3+ exhibits outstanding quantum efficiency (74.7%). It reveals that Ca3Hf2SiAl2O12: xCe3+ possesses remarkable optical properties and can be utilized in UV-LEDs.
Co-reporter:Qian Wang, Ge Zhu, Shuangyu Xin, Xin Ding, Ju Xu, Yuansheng Wang and Yuhua Wang
Physical Chemistry Chemical Physics 2015 vol. 17(Issue 41) pp:27292-27299
Publication Date(Web):21 Jul 2015
DOI:10.1039/C5CP02899J
A blue-emitting phosphor BaSc2Si3O10:Eu2+ was synthesized using the conventional solid-state reaction. The crystallographic occupancy of Eu2+ in the BaSc2Si3O10 matrix was studied based on the Rietveld refinement results and the photoluminescence properties. BaSc2Si3O10 exhibits blue emission ascribed to 3T2–1A1 and 3T1–1A1 charge transfer of SiO44− excited by 360 nm. All the phosphors of BaSc2Si3O10:Eu2+ exhibit strong broad absorption bands in the near ultraviolet range, and give abnormal blue emission upon 330 nm excitation. The abnormal phenomenon was explored in detail through many pieces of experimental evidence. The concentration of Eu2+ is optimized to be 3 mol% according to emission intensity and the quenching mechanism is verified to be a quadrupole–quadrupole interaction. The CIE coordinates of BaSc2Si3O10:0.03Eu2+ are calculated to be (0.15, 0.05) and BaSc2Si3O10:0.03Eu2+ shows similar thermal stability to commercial BaMgAl10O17:Eu2+.
Co-reporter:Xicheng Wang, Zhengyan Zhao, Quansheng Wu, Yanyan Li, Chuang Wang, Aijun Mao and Yuhua Wang
Dalton Transactions 2015 vol. 44(Issue 24) pp:11057-11066
Publication Date(Web):01 May 2015
DOI:10.1039/C5DT00800J
A series of SrSiAl2O3N2:Eu2+ (0.005 ≤ x ≤ 0.05) phosphors were successfully synthesized through a pressureless, facile, and efficient solid state route. The crystal structure, band structure, and their photoluminescence and cathodoluminescence properties were investigated in detail. The phosphors exhibit rod shape morphology with a uniform Eu2+ distribution. Under n-UV excitation the emission spectra shift from 477 to 497 nm with an increase of Eu2+ concentration. The concentration quenching mechanism of Eu2+ emission was dominated by the dipole–dipole interaction. The thermal stability is comparable to that of the commercial Ba2SiO4:Eu2+ phosphor. The phosphor also exhibits high current saturation and high resistance under low voltage electron bombardment. All the results indicate that the SrSiAl2O3N2:Eu2+ phosphors can be considered as candidates for application in both white LEDs and FEDs.
Co-reporter:Wenjin Xu, Ge Zhu, Xufeng Zhou and Yuhua Wang
Dalton Transactions 2015 vol. 44(Issue 19) pp:9241-9250
Publication Date(Web):13 Apr 2015
DOI:10.1039/C5DT00866B
A novel phosphate Ca9La(GeO4)0.75(PO4)6 was investigated to add to the family of phosphate phosphors and application in LEDs. In this work, the single phase red-emission Ce3+,Mn2+ co-doped phosphate Ca9La(GeO4)0.75(PO4)6 phosphor was synthesized by the solid-state reaction from both theoretical and practical points of view. The crystal structure was determined by Rietveld refinement and TEM. Its cell parameters are a = b = 10.4077605(2) Å, and c = 37.4714968(1) Å. The characteristic photoluminescence properties were studied in detail using photoluminescence excitation spectra, emission spectra, decay times and thermal quenching properties. Purple and red broad band emission from Ce3+ and Mn2+ was detected under excitation at 313 nm. According to this research, the Ca9La(GeO4)0.75(PO4)6:Ce3+,Mn2+ phosphor shows high thermal stability in the red-emission area. With the increase of the temperature, the intensity ratio of Mn2+ and Ce3+ emission rises rapidly and the purity of red-emission is improved. In order to reasonably explain this special phenomenon, an implicit mechanism between thermal quenching and energy transfer is proposed based on the configurational coordinate diagram. In addition, the mechanism could be helpful for understanding the thermal properties of multiple activators Ce3+ and Mn2+ co-doped phosphors as the reference.
Co-reporter:Chuang Wang, Zhengyan Zhao, Quansheng Wu, Ge Zhu and Yuhua Wang
Dalton Transactions 2015 vol. 44(Issue 22) pp:10321-10329
Publication Date(Web):27 Apr 2015
DOI:10.1039/C5DT00815H
The promising green oxynitride phosphor, Ba3−xMgxSi6O12N2:Eu2+ was synthesized by the solid-state reaction method. The effect of Mg2+ doping on the structure and photoluminescence (PL) properties of Ba3Si6O12N2:Eu2+ was investigated systematically. The results reveal that the phosphor retains the single phase of Ba3Si6O12N2, with the lattice expanding upon increasing the Mg2+ concentration, in an appropriate range. This suggests that a large portion of Mg2+ enters into the interstitial sites of the crystal lattice. At a certain concentration, Mg2+ doping can greatly enhance the absorption and PL intensity and decrease the full widths at half maximum (FWHM) of Ba3Si6O12N2:Eu2+ phosphors. The green phosphor Ba2.87Eu0.1Mg0.03Si6O12N2 exhibited a small thermal quenching, which remained 82% of the initial emission intensity when measured at 150 °C. The quantum efficiency measured at 400 nm excitation was 38.5%. All the results indicate that the solid solution Ba3−xMgxSi6O12N2:Eu2+ can be a good candidate for phosphors applicable in n-UV LEDs for solid-state lighting.
Co-reporter:Shuangyu Xin, Yuhua Wang, Ge Zhu, Xin Ding, Wanying Geng and Qian Wang
Dalton Transactions 2015 vol. 44(Issue 36) pp:16099-16106
Publication Date(Web):05 Aug 2015
DOI:10.1039/C5DT02099A
A novel phosphate RbZnPO4 has been developed for the first time and the characteristic crystal structure of RbZnPO4 has been investigated in detail, based on the Fourier transform infrared reflection spectra and the structure refinement of X-ray diffraction data. After doping with Eu3+,RbZnPO4:Eu3+ shows distinctive deep red emission with dominating peaks at 596 and 701 nm. To provide a reasonable explanation for the relationship between photoluminescence and structure, the photoluminescence property has been discussed by analyzing the particular local ligand environment and site occupation of Eu3+ in RbZnPO4. More interestingly, temperature-sensitive emission behavior was found in RbZnPO4:Eu3+. Through the synthetical analysis of the configurational coordinate diagram, the charge compensation experiment and the CASTEP band structure calculation, a complex underlying mechanism is proposed to explain the abnormal temperature-sensitive emission behavior in RbZnPO4:Eu3+. The mechanism could be helpful for better understanding the thermal quenching process of Eu3+ in RbZnPO4 and also as a reference in some other temperature-sensitive phosphors.
Co-reporter:Jianyan Ding, Quansheng Wu, Yanyan Li, Qiang Long, Chuang Wang and Yuhua Wang
Dalton Transactions 2015 vol. 44(Issue 20) pp:9630-9636
Publication Date(Web):08 Apr 2015
DOI:10.1039/C5DT00907C
In this study, a series of novel single-phased white light-emitting phosphors, Sr(7.3−x/2−y/2)Ca(2.7−x/2−y/2)(PO4)6F2:xEu2+,yMn2+ (0 ≤ x ≤ 0.06, 0 ≤ y ≤ 0.9) (SCPF:xEu2+,yMn2+), have been successfully prepared through a high temperature solid-state reaction. The crystal structure and photoluminescence have been measured and analyzed. The energy transfer mechanism is demonstrated to be a quadrupole–quadrupole interaction and the critical distance between the Eu2+ and Mn2+ has been calculated. Meanwhile, the efficiency η of the energy transfer from Eu2+ to Mn2+ can reach 76%. The excitation spectra monitored at 457 nm ranges from 290 nm to 400 nm. Under excitation at 365 nm, the emission spectra include two broad bands peaked at 458 nm and 570 nm. By changing the ratio of Eu2+/Mn2+, the emission color can change from blue to white. Furthermore, our results give the Commission International de L'Eclairage (CIE) chromaticity coordinates for the white LED as (0.334, 0.307) and a correlated color temperature of 3982 K, which indicates that the SCPF:Eu2+,Mn2+ phosphor is a very promising candidate for use as a near ultraviolet (NUV) white light-emitting diode (WLED) phosphor.
Co-reporter:Yurong Shi, Ge Zhu, Masayoshi Mikami, Yasuo Shimomura and Yuhua Wang
Dalton Transactions 2015 vol. 44(Issue 4) pp:1775-1781
Publication Date(Web):24 Nov 2014
DOI:10.1039/C4DT03144J
A novel Ce3+ activated Lu3MgAl3SiO12:Ce phosphor was synthesized and found to crystallize in the garnet structure. The crystal structure of the synthesized phosphor has been characterised by X-ray diffraction and Rietveld refinement. Both room and high temperature photoluminescence spectra are utilized to investigate the luminescence properties and crystal field splitting. The high temperature quenching of these phosphors and their quantum efficiency (QE) are also studied using both the prepared YAG:Ce and the commercial YAG:Ce phosphor named P46-y3 as the reference. Upon excitation with blue light, the composition-optimized Lu3MgAl3SiO12:Ce phosphor exhibited strong yellow light with a high QE of 81.2% and better thermal stability than that of the commercial phosphor. The results indicate that the Lu3MgAl3SiO12:Ce phosphor can serve as a candidate for blue chip LEDs.
Co-reporter:Qinping Qiang, Wenbo Chen, Xinlong Ma and Yuhua Wang
Dalton Transactions 2015 vol. 44(Issue 13) pp:6242-6248
Publication Date(Web):19 Feb 2015
DOI:10.1039/C4DT03690E
A series of x mol% Yb3+, 1 mol% Ho3+/1 mol% Er3+ (0 ≤ x ≤ 25) codoped BaLiF3 microcrystals with different cubic morphologies and sizes (1.52 μm–3.83 μm) were synthesized by a facile surfactant-assisted hydrothermal-microemulsion approach for the first time. The crystalline structure of BaLiF3 was established via the Rietveld refinement result of the powder X-ray diffraction (XRD) data. In addition, the growth process of cubic BaLiF3 crystals and the influence of different synthesis conditions on the morphology were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, in this paper we first investigated the upconversion luminescence (UCL) properties of new Er3+/Ho3+, Yb3+-codoped BaLiF3 microcrystals under 980 nm excitation. The characteristic emission of Er3+ and Ho3+ was obtained, respectively. The blue emission in BaLiF3:Yb3+, Ho3+ which was comparatively more difficult to discover was also observed and explained by the energy level diagram. It is worthwhile to point out that BaLiF3:Yb3+, Er3+ practically showed pure red upconversion (UC) emission under excitation at 980 nm and the reasons behind this behavior are presented and discussed.
Co-reporter:Gen Li, Yuhua Wang, Wei Zeng, Wenbo Chen, Shaochun Han and Haijie Guo
RSC Advances 2015 vol. 5(Issue 27) pp:20884-20889
Publication Date(Web):10 Feb 2015
DOI:10.1039/C4RA17019A
Novel afterglow phosphors based on the GdSr2AlO5 host were prepared by solid-state reaction under reductive atmosphere. The photoluminescence, afterglow, thermoluminescence and magnetism properties of GdSr2AlO5:RE3+ (RE3+ = Eu3+, Sm3+, Pr3+ and Dy3+) were discussed in detail for the first time in this paper. By doping appropriate rare earth ions into the GdSr2AlO5 host, all phosphors showed a satisfactory long-wavelength afterglow phenomenon and excellent paramagnetism characteristics. The mass magnetic susceptibility value was determined to be approximately 4.4052 × 10−5 emu g−1 Oe−1.
Co-reporter:Xin Ding, Ge Zhu, Qian Wang and Yuhua Wang
RSC Advances 2015 vol. 5(Issue 38) pp:30001-30004
Publication Date(Web):12 Mar 2015
DOI:10.1039/C5RA03323C
A novel rare-earth free green-emitting KAlSi2O6:Mn2+ phosphor is synthesized by traditional solid-state reaction. The structure, photoluminescence and temperature-dependent properties are investigated. KAlSi2O6:Mn phosphor can emit green light peaking at 513 nm with narrow full-width at half-maximum of 30 nm upon 450 nm excitation. The quantum yields and Commission Internationale de I’Eclairage (CIE) color coordinates are 30.2% and (0.27, 0.64). The white LED is fabricated by KAlSi2O6:Mn and CaAlSiN3:Eu (red phosphor) combined with blue LED chip. Its correlated color temperature, color coordinates, Ra and luminous efficiency are 4775 K, (0.35, 0.36), 85.1 and 110.2 lm W−1, respectively. It is demonstrated that KAlSi2O6:Mn2+ phosphor as the potential material could be simulated to blue-LED for producing efficient white-light.
Co-reporter:Lingzhi Hu, Qian Wang, Xicheng Wang, Yang Li, Yuhua Wang and Xingping Peng
RSC Advances 2015 vol. 5(Issue 127) pp:104708-104714
Publication Date(Web):20 Nov 2015
DOI:10.1039/C5RA18558K
Mn2+-doped Na2MgGeO4 green phosphors were prepared using a solid-state reaction method. X-ray diffraction, scanning electron microscopy, and photoluminescence (PL) and cathodoluminescence (CL) studies were utilized to characterize the prepared phosphors. Under UV radiation (297 nm), the Na2MgGeO4:0.03Mn2+ phosphor showed a strong green emission corresponding to the 4T1(4G)–6A1(6S) transition of the Mn2+ ions. A possible interaction mechanism was investigated. The CL spectra as a function of accelerating voltage and probe current were also measured. Under continuous low-voltage electron-beam excitation, the phosphor exhibited excellent degradation properties and good color stability. The results indicate that the Na2MgGeO4:0.03Mn2+ phosphor could be a suitable green phosphor candidate for FEDs.
Co-reporter:Si Chen, Jiangtao Chen, Jianlin Liu, Jing Qi, Yuhua Wang
Applied Surface Science 2015 Volume 357(Part A) pp:413-416
Publication Date(Web):1 December 2015
DOI:10.1016/j.apsusc.2015.09.030
Highlights
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High temperature O2 annealing degrades the FE properties of ZnO nanowire arrays.
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Degraded FE properties are mainly caused by changes of oxygen vacancy densities.
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PL properties changed significantly after oxygen annealing and followed FE measuring.
Co-reporter:Wang Chuang, Xin Shuangyu, Wang Xicheng, Zhu Ge, Wu Quansheng and Wang Yuhua
New Journal of Chemistry 2015 vol. 39(Issue 9) pp:6958-6964
Publication Date(Web):01 Jul 2015
DOI:10.1039/C5NJ00997A
A series of Sr2−xLaxSi5−xAlxN8:Eu2+ nitride phosphors were synthesized by the gas-pressed sintering method. The influence of La3+–Al3+ incorporation into Eu2+-doped Sr2Si5N8 phosphors on the crystal structure and luminescence properties was discussed in this work. X-ray diffraction with Rietveld refinements, photoluminescence spectra, thermal quenching behavior, and lifetimes were utilized to characterize the samples. More interestingly, an additional emission band located at lower-energy was observed under near-ultraviolet excitation, which is different from previous literature. Under the excitation of near-ultraviolet, the emission color for the La3+–Al3+ substitutions can be tuned from orange-red to red. The mechanism of the additional emission band located at lower-energy and the thermal quenching behavior are discussed too. This mechanism can efficiently tune optical properties, especially thermal stability, and could be general to luminescent materials.
Co-reporter:Shanshan Du, Deyin Wang, Yuhua Wang, Shuangyu Xin, QinPing Qiang and Xinlong Ma
New Journal of Chemistry 2015 vol. 39(Issue 7) pp:5605-5611
Publication Date(Web):12 May 2015
DOI:10.1039/C5NJ00913H
Samples of Ca9Y(PO4)7 co-doped with Yb3+/Er3+, Yb3+/Tm3+, or Yb3+/Er3+/Tm3+ have been synthesized through two different routes, i.e. a modified hydrothermal method, followed by annealing in air at 850 °C and a solid-state reaction. The results of SEM and TEM show that the particle size of the samples synthesized by the solid state reaction method is about several micrometers, while that of the sample synthesized by the modified hydrothermal method is around 180 nm. The up-conversion luminescence of samples is studied as a function of different Yb3+, Er3+, Tm3+ ion concentrations and laser powers. Under 980 nm laser excitation, samples of Yb3+/Er3+ co-doped Ca9Y(PO4)7 generate green and red emissions, while samples co-doped by Yb3+/Tm3+ generate blue and red emissions. The red emission is most intense in Yb3+/Er3+ co-doped samples, while blue emission is predominant in Yb3+/Tm3+ co-doped samples. The main mechanism that allows for the up-conversion observed in Yb3+/Er3+, Yb3+/Tm3+ or Yb3+/Er3+/Tm3+ doped Ca9Y(PO4)7 is attributed to the energy transfer among Yb3+ and the various Er3+/Tm3+ ions in excited states.
Co-reporter:Xin Ding, Wanying Geng, Qian Wang and Yuhua Wang
RSC Advances 2015 vol. 5(Issue 119) pp:98709-98716
Publication Date(Web):09 Nov 2015
DOI:10.1039/C5RA20631F
A series of color-adjustable phosphors Ca3Hf2SiAl2O12:Ce3+,Mn2+ were synthesized through a high temperature solid-state method. Ca3Hf2SiAl2O12 belongs to body-centered cubic crystal system and Iad (230) space-group. It was found that three different cation sites in the Ca3Hf2SiAl2O12 phase were occupied evenly by Ce3+ and Mn2+ ions. Different situations of Mn2+ occupying sites and energy transfer from Ce3+ to Mn2+ can appear with different Mn2+ content and the critical distance was calculated to be Rc1 = 10.8 Å, Rc2 = 10.1 Å and Rc3 = 12.6 Å after calculation of energy transfer from the Ce3+ to Mn2+ by using the concentration quenching method. Ca3Hf2SiAl2O12:Ce3+,Mn2+ phosphors exhibited a broad excitation band ranging from 300 to 450 nm and two broad asymmetric emission bands upon 400 nm excitation. The emission colors of Ca3Hf2SiAl2O12:Ce3+,Mn2+ could be tuned from blue-green (0.2303, 0.3265) to white (0.3350, 0.3388) by changing the ratio of Ce3+/Mn2+. The correlated color temperature can be adjusted from 12763 K to 5379 K. It indicated that Ca3Hf2SiAl2O12:Ce3+,Mn2+ possesses potential applications in white-LEDs.
Co-reporter:Yaxin Cao, Ge Zhu and Yuhua Wang
RSC Advances 2015 vol. 5(Issue 81) pp:65710-65718
Publication Date(Web):27 Jul 2015
DOI:10.1039/C5RA10435A
In order to explore a new kind of red phosphor for near ultraviolet white light emitting diodes (NUV-WLEDs) and field emission displays (FEDs), Eu3+ doped NaLa9(GeO4)6O2 was synthesized and its luminescence properties were studied for the first time for fundamental research. The results indicate that all samples crystallize in the hexagonal crystal system with the P63/m space group. Eu3+ doped NaLa9(GeO4)6O2 with the content of 0.07 has optimal photoluminescence properties, with a dominant red emission peak at 612 nm (5D0–7F2) with CIE coordinates of (0.64, 0.35) under 392 nm excitation and the quantum efficiency of 45.2%. Additionally, the thermal quenching property has been studied and its possible mechanism has also been expounded. Furthermore, the cathodoluminescence (CL) property was investigated and the result reveals that the sample has excellent degradation properties for FEDs. The study reveals that NaLa9(GeO4)6O2:0.07Eu3+ could be a suitable red-emitting phosphor candidate for NUV-WLEDs and FEDs.
Co-reporter:Quansheng Wu, Jianyan Ding, Chuang Wang, Yanyan Li, Xicheng Wang, Aijun Mao and Yuhua Wang
RSC Advances 2015 vol. 5(Issue 40) pp:31255-31261
Publication Date(Web):17 Mar 2015
DOI:10.1039/C5RA01300C
The solid solutions of nitridosilicate phosphors LiSi2N3:Eu-xAlN (0 ≤ x ≤ 0.35) were synthesized using a gas-pressed sintering in this work. The effects of a solid solution of AlN on crystal structure, morphology, thermal stability and luminescence properties were studied. The luminescence intensity of LiSi2N3:Eu phosphor is significantly improved by the solution of AlN, but the emission position is unchanged. The emission intensity of LiSi2N3:Eu0.01-0.30AlN is about 2.17 times that of LiSi2N3:Eu0.01. The results show that these solid solutions could be the most useful way to improve the luminescence intensity of LiSi2N3:Eu phosphors.
Co-reporter:Qian Wang, Ge Zhu, Yanyan Li, Yuhua Wang
Optical Materials 2015 Volume 42() pp:385-389
Publication Date(Web):April 2015
DOI:10.1016/j.optmat.2015.01.032
•The luminescent properties of Y2WO6: Pr3+ was investigated for first time.•The emission color of Y2WO6: xPr3+ is adjustable excited by different excitation wavelengths.•The thermal properties of Y2WO6: Pr3+ was investigated in detail.A series of Pr3+ activated Y2WO6 phosphors are prepared by solid state reaction method. The crystalline phase and luminescent properties of samples are discussed by X-ray diffraction spectra and photoluminescence spectra, respectively. The photoluminescence excitation spectrum indicates that the sample can absorb both UV and blue light. And the samples emit a blue emission of WO66− and the characteristic red emission of Pr3+. The partial quenching of the other prominent blue luminescence from 3P0 state is ascribed to a radiationless relaxation pathway involving a low-lying Pr4+–W5+ intervalence charge transfer (IVCT) state. Through adjusting the excitation wavelength, Y2WO6: Pr3+ can not only emit warm white light with CIE coordinates of (0.33, 0.37) but also show bright red emission with CIE coordinates of (0.66, 0.33). In addition, the thermal properties of the samples are also investigated in detail. The results show that the application as a white and red component for white light emitting diodes is proposed.
Co-reporter:Wenrui CHANG, Dan WANG, Xingping PENG, Yuhua WANG, Lingzhi HU, Jing WANG
Journal of Rare Earths 2015 Volume 33(Issue 5) pp:480-485
Publication Date(Web):May 2015
DOI:10.1016/S1002-0721(14)60444-0
A series of color-tunable KLaSiO4:Ce3+,Mn2+ phosphors were successfully prepared and the luminescent properties were investigated. Upon excitation at 290 nm, the emission spectra of KLaSiO4:Ce3+,Mn2+ phosphors included a blue emission band and a red emission band. Increasing the doping concentration of Mn2+ ions, the red emission was strengthened considerably, and the blue emission of Ce3+ was reduced, owing to the efficient energy transfer. The composition optimized KLa0.96SiO4:0.02Ce3+,0.02Mn2+ sample exhibited the white light emission brightly with the chromaticity coordinates of (0.331, 0.337). Therefore, KLaSiO4:Ce3+, Mn2+ could be used as a white phosphor candidate for white light-emitting diodes devices.Emission spectra of Ce3+ and Mn2+ in the KLa(0.98-y)SiO4: 0.02Ce3+,yMn2+ (0=y=0.10) phosphors with various Mn2+ concentrations under an excitation wavelength of 290 nm (the inset shows the energy levels diagram of the Ce3+-Mn2+ couple)
Co-reporter:Xicheng Wang
The Journal of Physical Chemistry C 2015 Volume 119(Issue 28) pp:16208-16214
Publication Date(Web):June 24, 2015
DOI:10.1021/acs.jpcc.5b01552
A novel garnet phosphor Ca2YZr2Al3O12:Ce3+ (CYZA:Ce3+) has been successfully designed and synthesized via the solid state method. The crystal structure, morphology, as well as their photoluminescence properties were investigated in detail. Under near-ultraviolet (n-UV) excitation, CYZA:Ce3+ exhibits cyan to green emission with the maxima from 484 to 503 nm when varying the Ce3+ concentration. The internal quantum efficiency of the optimal sample is 56%. The concentration quenching of Ce3+ emission occurs via the energy transfer among the nearest-neighbor ions. The thermal stability is superior compared with the Ba2SiO4:Eu2+ commercial phosphor. These results suggest that CYZA:Ce3+ can be considered as a potential candidate for white LEDs.
Co-reporter:Quansheng Wu, Yuhua Wang, Zhigang Yang, Meidan Que, Yanyan Li and Chuang Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 5) pp:829-834
Publication Date(Web):30 Oct 2013
DOI:10.1039/C3TC31471E
Pure nitride Ca-α-sialon phosphors with the composition Ca1.4−xAl2.8Si9.2N16:xEu (x = 0–0.3) were successfully prepared by gas-pressed sintering and their luminescence properties and morphology were investigated. Simultaneously, their time-resolved spectra were also presented. Ca1.4Al2.8Si9.2N16:Eu exhibited broad-band yellow-orange emission centered at ∼592 nm (FWHM ≈ 85 nm) under 400 nm excitation and with good thermal stability. Its emission intensity at 250 °C remained 88% of that measured at room temperature. The emission intensity was 1.7 times that of YAG:Ce3+ (P46-Y3) commercial phosphor. The outstanding luminescent properties allow it to be an attractive luminescent material for white LEDs.
Co-reporter:Xicheng Wang, Takatoshi Seto, Zhengyan Zhao, Yanyan Li, Quansheng Wu, Hao Li and Yuhua Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 22) pp:4476-4481
Publication Date(Web):25 Mar 2014
DOI:10.1039/C4TC00190G
A series of quaternary nitride solid solutions with a general formula of Sr1−xCaxYSi4N7:Eu2+ (1 atom%) were synthesized by the carbothermal reduction and nitridation (CRN) method. The XRD patterns confirm the formation of a solid solution of Sr1−xCaxYSi4N7:Eu2+ (0 ≤ x ≤ 0.5). With an increase in x, the emission spectra shift from 540 nm to 564 nm under n-UV excitation. In addition, the temperature dependence of the PL intensity was investigated. The thermal stability is comparable to that of the commercial (Ba,Sr)2SiO4:Eu2+ phosphor. All the results indicate that the solid solution Sr1−xCaxYSi4N7:Eu2+ can be a good candidate of phosphor applicable to n-UV LEDs for solid-state lighting.
Co-reporter:Lili Han, Yuhua Wang, Linna Guo, Lei Zhao and Ye Tao
Nanoscale 2014 vol. 6(Issue 11) pp:5907-5917
Publication Date(Web):01 Apr 2014
DOI:10.1039/C4NR00512K
A facile, hydrothermal/solvothermal route has been developed to synthesize a series of multifunctional lanthanide ion (Tb3+, Eu3+, Yb3+, Tm3+, Er3+ and Ho3+)-activated ScF3 nanocrystals. The morphology and size of ScF3 can be tuned in a controlled manner by altering the additives and volume ratios of H2O:EtOH in the initial solution. Under ultraviolet (UV), vacuum ultraviolet (VUV) or low-voltage electron-beam excitation, the as-obtained Tb3+, Eu3+ codoped ScF3 product exhibits multicolor photoluminescence (PL) and cathodoluminescence (CL), and possible luminescence mechanisms are discussed. Moreover, under 980 nm excitation, upconversion (UC) emissions have been achieved in Yb3+–Er3+, Yb3+–Tm3+, and Yb3+–Ho3+ codoped ScF3. Ferromagnetic property of ScF3 is detected due to the nanocrystal defects. The results obtained indicate that the lanthanide ion-doped ScF3 nanocrystals exhibit multicolor UV/VUV PL, CL, and UC luminescence as well as ferromagnetic properties. Thus, they may have potential applications in PL areas, field emission display devices, bioseparation and magnetic resonance imaging.
Co-reporter:Quansheng Wu, Xicheng Wang, Zhengyan Zhao, Chuang Wang, Yanyan Li, Aijun Mao and Yuhua Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 37) pp:7731-7738
Publication Date(Web):23 Jul 2014
DOI:10.1039/C4TC01131G
A green-emitting nitride phosphor Ca1.4Al2.8Si9.2N16:Ce3+, Li+ (CASN:Ce) has been successfully synthesized which is applicable to near-ultraviolet based light-emitting diodes (LEDs) and field emission displays (FEDs). The characteristic photoluminescence (PL) properties were studied in detail by PL excitation, emission spectra and time-resolved spectroscopy. CASN:0.10Ce exhibits broad-band green emission centered at ∼525 nm (FWHM ≈ 135 nm) under 395 nm excitation and with excellent thermal stability. The effect of host lattice composition on PL properties was also discussed. The cathodoluminescence (CL) spectra as a function of accelerating voltage and probe current were also studied. Excellent degradation resistance properties with good color stability were obtained by continuous low-voltage electron-beam excitation of the phosphor.
Co-reporter:Linna Guo, Yuhua Wang, Zehua Zou, Bing Wang, Xiaoxia Guo, Lili Han and Wei Zeng
Journal of Materials Chemistry A 2014 vol. 2(Issue 15) pp:2765-2772
Publication Date(Web):28 Jan 2014
DOI:10.1039/C3TC32540G
A series of ErF3 samples with different morphologies (flake, truncated octahedral, flower-like and rice-like microcrystals) and sizes (20 nm–2 μm) were prepared by an aqueous-based hydrothermal and coprecipitation route, respectively. The crystal structure of ErF3 is firstly established via the Rietveld refinement result of the powder XRD data. In addition, the ErF3 matrix without doping sensitizer or activator shows bright red upconversion emission under excitation at 980 nm. It is worthwhile pointing out that ErF3 with an octahedral morphology demonstrates the highest relative intensity, with that of flower-like microcrystals following, but the nanoflakes show the lowest intensity, and the relative intensity is almost 8 times as low as that of the microcrystals. Further doping with Li+ would enhance the upconversion luminescence intensity, and the upconversion emission intensity of the optimal sample with doping 6 mol% Li+ is four times stronger than that of a Li+ free sample. Furthermore, upon electron beam excitation, the cathodoluminescence properties of a ErF3 matrix as a new upconversion host are also studied, which is an interesting phenomenon.
Co-reporter:Quansheng Wu, Zhigang Yang, Zhengyan Zhao, Meidan Que, Xicheng Wang and Yuhua Wang
Journal of Materials Chemistry A 2014 vol. 2(Issue 25) pp:4967-4973
Publication Date(Web):18 Mar 2014
DOI:10.1039/C3TC32422B
A near-UV excited phosphor, Y4Si2O7N2:Ce3+, was synthesized using a solid-state reaction. The crystal structure and luminescence properties were studied. Y4Si2O7N2 crystallizes in a monoclinic unit cell with space group P21/c, lattice constants a = 7.5678(2) Å, b = 10.4529(1) Å, c = 10.7779(3) Å and β = 110.06°, and cell volume = 800.85(2) Å3. The crystal structure of Y4Si2O7N2, featuring Si(O,N)4 polyhedra, is provided, and there are four different Y3+ coordination environments with two different coordination numbers in the structure. Ce3+-doped Y4Si2O7N2 exhibited a broad emission band, and the maximum emission wavelength could be tuned from blue (λem = 450 nm) to green (λem = 515 nm) by increasing the concentration of Ce3+. The quantum efficiency was determined to be about 47%. The results show that Y4Si2O7N2:Ce3+ is a candidate for use as a conversion phosphor for near-UV white LED applications.
Co-reporter:Yanyan Li, Yurong Shi, Ge Zhu, Quansheng Wu, Hao Li, Xicheng Wang, Qian Wang, and Yuhua Wang
Inorganic Chemistry 2014 Volume 53(Issue 14) pp:7668-7675
Publication Date(Web):June 26, 2014
DOI:10.1021/ic500963q
A series of single-component Ce3+, Li+, Mn2+ ions codoped color-tunable CaSr2Al2O6 phosphors were synthesized by a high-temperature solid-state reaction, and the photoluminescence properties as well as the energy transfer mechanism from Ce3+ to Mn2+ ions have been investigated in detail. The Ce3+ activated phosphors have strong absorption in the range of 250–420 nm and can give a blue emission centered at about 460 nm. When Mn2+ ions are codoped, the emission of CaSr2Al2O6:Ce3+, Li+, Mn2+ phosphors can be tuned from blue to red through adjusting the doping concentration of the Mn2+ ions, under the irradiation of 358 nm. When the concentration of Mn2+ is increased to 0.02, a warm-white light can be obtained with good CIE coordinates of (0.388, 0.323) and a low CCT of 3284 K. The energy transfer mechanism from the Ce3+ to Mn2+ ions is demonstrated to be a quadrupole–quadrupole interaction based on the analysis of the decay curves of the phosphors. The thermal quenching stability was also investigated. The results indicate that CaSr2Al2O6:Ce3+, Li+, Mn2+ samples might have potential applications in w-LEDs.
Co-reporter:Zhipeng Ci, Meidan Que, Yurong Shi, Ge Zhu, and Yuhua Wang
Inorganic Chemistry 2014 Volume 53(Issue 4) pp:2195-2199
Publication Date(Web):January 28, 2014
DOI:10.1021/ic402859s
Co-reporter:Chuang Wang, Zhengyan Zhao, Quansheng Wu, Shuangyu Xin and Yuhua Wang
CrystEngComm 2014 vol. 16(Issue 41) pp:9651-9656
Publication Date(Web):27 Aug 2014
DOI:10.1039/C4CE01364F
The promising green oxynitride phosphor, Ba3−xCaxSi6O12N2:Eu2+, was synthesized at 1350 °C for 5 hours under a reducing N2/H2 (5%) atmosphere via the solid-state reaction method. The XRD patterns confirm the formation of the pure phase of Ba3−xCaxSi6O12N2:Eu2+. With an increase in x, the emission spectra shift from 525 nm to 536 nm under near-UV (n-UV) excitation. Accordingly, we propose the underlying mechanisms for the red-shift of the emission spectra by adjusting the cation composition in the host. The influence of the size mismatch on the thermal quenching is also observed. The as-prepared green phosphor exhibits great thermal quenching property, with the remaining 83% of the initial emission intensity measured at 150 °C. The quantum efficiency is measured to be 35.2%. All the results indicate that the Ba3−xCaxSi6O12N2:Eu2+ can be a good candidate phosphor applicable to n-UV light-emitting diodes for solid-state lighting.
Co-reporter:Ge Zhu, Yurong Shi, Masayoshi Mikami, Yasuo Shimomura and Yuhua Wang
CrystEngComm 2014 vol. 16(Issue 27) pp:6089-6097
Publication Date(Web):01 May 2014
DOI:10.1039/C4CE00523F
As new light sources for next-generation illumination, white light-emitting diodes (LEDs) have been developed extensively and are commercially available due to their excellent advantages. However, the current white LEDs present in the market based on the combination of a blue chip and a yellow phosphor cannot satisfy the need for indoor illumination or some other colourful fields due to the lack of a sufficient red spectral component. Here we report a green phosphor, NaBaScSi2O7:Eu2+, which can be effectively excited using a near-ultraviolet chip and emit bright green light with extremely excellent thermal stability. The electronic structure and characteristic photoluminescence and cathodoluminescence properties as well as the thermal quenching properties were investigated in detail. The origin of the desired green luminescence was also determined by analyzing the crystal structure and measuring fluorescence lifetimes and the site-selective excitation and emission spectra. In addition, to investigate its application in field emission displays, the cathodoluminescence (CL) spectra of NaBaScSi2O7:Eu2+ as a function of the accelerating voltage, probe current and the electron radiation time were also measured and discussed in detail. The current results indicate that NaBaScSi2O7:Eu2+ can serve as a potential green phosphor for application in high-power white LEDs and field emission displays.
Co-reporter:Yurong Shi, Yan Wen, Meidan Que, Ge Zhu and Yuhua Wang
Dalton Transactions 2014 vol. 43(Issue 6) pp:2418-2423
Publication Date(Web):31 Oct 2013
DOI:10.1039/C3DT52405A
A rare-earth free red emitting β-Zn3B2O6:Mn2+ phosphor was prepared by a solid-state reaction method. The crystal structure, photoluminescent and cathodoluminescent properties of β-Zn3B2O6:Mn2+ were systematically investigated. The absorption and photoluminescence excitation spectra confirm that β-Zn3B2O6:Mn2+ matches the UV LED chip. Under UV light and low-voltage electron beam excitations, an interesting orange-red emission band centered at ∼600 nm of Mn2+ at the tetrahedral Zn2+ sites is observed. Besides, the unusual red shift with increasing Mn2+ content is also found and contributed to an exchange interaction between Mn2+. In addition, under low-voltage excitation, β-Zn3B2O6:Mn2+ exhibits higher color purity of 98.1% than that of the commercial ZnS:Ag,Cd yellow phosphor and reported ZnGeN2:Mn2+ orange phosphor, which indicated the β-Zn3B2O6:Mn2+ has a patenting application in FEDs.
Co-reporter:Quansheng Wu, Yanyan Li, Xicheng Wang, Zhengyan Zhao, Chuang Wang, Hao Li, Aijun Mao and Yuhua Wang
RSC Advances 2014 vol. 4(Issue 73) pp:39030-39036
Publication Date(Web):20 Aug 2014
DOI:10.1039/C4RA05502K
Eu2+ doped and Eu2+, Ce3+ co-doped LiSi2N3 phosphors were successfully prepared by gas-pressed sintering in this study. The dominant excitation band of LiSi2N3:Eu2+ was found at about 355 nm and exhibited a broad-band yellow emission centered at 592 nm instead of the early reports of 310 nm and 580 nm, respectively. The shifting behavior dominantly contributed to different oxygen content in the host. The second luminescent center formed by the introduction of oxygen into nitride phosphors was discussed in detail. The detailed energy transfer mechanism from Ce3+ to Eu2+ in the LiSi2N3 host is also reported and a notable unusual redshift behavior was observed in Eu2+, Ce3+ co-doped LiSi2N3 phosphors.
Co-reporter:Hao Li, Bin Liu, Yuhua Wang, Shu Yin, Xinlong Ma, Xicheng Wang, Quansheng Wu, Runfen shen and Hang Chen
RSC Advances 2014 vol. 4(Issue 72) pp:37992-37997
Publication Date(Web):18 Aug 2014
DOI:10.1039/C4RA05126B
A series of B-doped graphene (BG)/rod-shaped TiO2 (RT) nanocomposites were firstly synthesized via a facile one-step hydrothermal reaction in NaBH4 aqueous solution. The photocatalytic activity of the obtained nanocomposites for the oxidative photo-destruction of NOX gas was investigated, and they showed better photocatalytic properties than pure TiO2 and graphene/TiO2 nanocomposites. This work could provide new insight into the fabrication of TiO2–carbon nanocomposites as high performance photocatalysts and facilitates their application in addressing environmental protection issues.
Co-reporter:Chuang Wang, Zhengyan Zhao, Xicheng Wang, Yanyan Li, Quansheng Wu and Yuhua Wang
RSC Advances 2014 vol. 4(Issue 98) pp:55388-55393
Publication Date(Web):15 Oct 2014
DOI:10.1039/C4RA04683H
Eu2+ doped Ca2Si5N8 phosphors were successfully prepared by gas-pressed sintering. The red-shift of the emission band from 608 nm to the longer wavelength 622 nm of the Ca2Si5N8:Eu2+ phosphor under blue excitation has been achieved, and a large enhancement in the emission intensity has been obtained by using BaF2. XRD data revealed that the lattice of Ca2Si5N8:Eu2+ was expanded with Ba2+ ion doping. XPS results suggested that there were more Eu2+ ions incorporated into the lattice of Ba2+ doped samples than those of the undoped samples. The doping effect of Ba2+ ions has been discussed in detail.
Co-reporter:Wei Zeng, Yuhua Wang, Shaochun Han, Wenbo Chen, Gen Li
Optical Materials 2014 Volume 36(Issue 11) pp:1819-1821
Publication Date(Web):September 2014
DOI:10.1016/j.optmat.2014.04.030
•We first discovered long-persistent luminescent phenomenon in a borate host (Ca2BO3Cl: Eu2+, Ln3+).•An excellent yellow emitting long-persistent luminescent was observed.•Thermoluminescence curves are studied to explain the long-persistent luminescent phenomenon.Ca2BO3Cl: Eu2+, Ln3+ (Ln = Nd, Dy, Er) phosphors have been synthesized through the high temperature solid-state method. The emission spectra reveal one asymmetric broad band located at 580 nm, ascribing to the 5d–4f transitions of Eu2+ ions in two different sites. The incorporation of Ln3+ ions, which act as trap centers, largely extends the thermoluminescence characteristics and evidently enhances the persistent luminescence property of phosphors. With the doping concentration of 0.1% Eu2+ and 0.1% Ln3+, afterglow of samples can persist over 3 h above recognizable intensity level (⩾0.32 mcd/m2).
Co-reporter:Wenbo Chen, Yuhua Wang, Wei Zeng, Shaochun Han, Gen Li
Optical Materials 2014 Volume 36(Issue 11) pp:1850-1854
Publication Date(Web):September 2014
DOI:10.1016/j.optmat.2014.04.039
•Persistent luminescence of Sr3Al2O5Cl2:Tb3+ were investigated for first time.•The filling of traps was investigated by changing the irradiation time.•The thermoluminescence properties for Sr3Al2O5Cl2:Tb3+ was investigated in detail.The Tb3+ doped Sr3Al2O5Cl2 phosphors have been synthesized via high temperature solid state reaction and their photoluminescence properties have been investigated. The Sr3Al2O5Cl2:Tb3+ samples emit a green luminescence from 5D4 to 7Fj (j = 6, 5, 4, 3) transition of Tb3+. The phosphorescence can be observed clearly by the naked eyes (0.32 mcd/m2) in the dark for over 1 h after 254 nm irradiation for the 5 min. Thermoluminescence (TL) measurements indicated that the TL glow curve was composed of the peaks located at 62, 142, 250 °C. The filling of traps was investigated by changing the irradiation time. Furthermore, the origin of long persistent luminescence has also been discussed.
Co-reporter:Linqin YE, Xingping PENG, Shuihe ZHANG, Yuhua WANG, Wenrui CHANG
Journal of Rare Earths 2014 Volume 32(Issue 12) pp:1109-1113
Publication Date(Web):December 2014
DOI:10.1016/S1002-0721(14)60190-3
Ca-doped BaMgAl10O17:Eu2+,Mn2+ (BAM) blue phosphors were synthesized by flux assisted solid-state reaction method using CaF2 and BaF2 as co-flux. Good dispersity and particle size homogenization of hexagonal pure phase BAM were obtained by sintering at 1400 °C. The effects of the Ca2+ ions content on the structure, morphology and photoluminescence properties of the phosphors were studied. The results indicated that the incorporation of Ca could decrease the lattice constant, improve the homogeneity and dispersity and enhance the photoluminescence (PL) intensity of the phosphor effectively. The optimum Ba0.86Ca0.04Mg0.97Al10O17:0.1Eu2+,0.03Mn2+ PL intensity was enhanced for about 30% and relative brightness was improved about 4%. Furthermore, the synthesized BAM and commercial BAM phosphors were annealed for 30 min at 600 °C in air. The Ca-doped phosphors had stronger emission intensity, higher brightness and better chromaticity stability than that of the commercial phosphor. These results indicated that Ca-doped blue phosphors had good potential applications in the commercial tricolor fluorescent lamps as well as in other display and lamps.(a) PL spectra of our BAM phosphors annealed at 600 °C for 30 min with different doping concentrations of CaF2 under 254 nm excitation (Numbers 1, 2, 3, 4, 5, 6 represent the same alphabets phosphors as shown in Fig. 3. Here, the number (1) sample has the similar PL intensity with commercial BAM. The maximal peak intensity is nearby 455 nm position with different CaF2 doping concentrations); (b) The relative brightness curves of commercial BAM (the red solid square in circle) and different CaF2 doped BAM
Co-reporter:Gen Li, Yuhua Wang, Wei Zeng, Shaochun Han, Wenbo Chen, Yanyan Li, Hao Li
Optical Materials 2014 Volume 36(Issue 11) pp:1808-1813
Publication Date(Web):September 2014
DOI:10.1016/j.optmat.2014.02.030
•A novel orange emitting LLP material based on LiSr4(BO3)3 was prepared successfully.•The band structure of LiSr4(BO3)3 were studied by calculation and experiment.•The introduction of Dy3+ had a great contribution to the afterglow performance.A novel orange emitting long-lasting phosphor based on LiSr4(BO3)3 host matrix was prepared by a solid-state reaction under a reductive atmosphere. Both diffuse reflectance spectra and photoluminescence emission spectra of the Eu2+-doped and Eu2+, Dy3+ co-doped samples revealed only the 5d–4f transitions of Eu2+. The broad emission band of Eu2+ appeared to be asymmetric, which illustrated only Eu2+ acted as the emission center in two different Sr sites. The duration of co-doped samples was prolonged drastically, compared with that of the Eu2+ single-doped samples. Investigation of thermoluminescence curves revealed that the incorporation of Dy3+ created more appropriate energy traps leading to the enhancement of afterglow.
Co-reporter:Xin Ding, Yurong Shi, Ge Zhu, Yuhua Wang
Materials Chemistry and Physics 2014 Volume 147(Issue 3) pp:351-355
Publication Date(Web):15 October 2014
DOI:10.1016/j.matchemphys.2014.05.038
•Investigate a mild method including three processes to get YAG: Ce3+.•YAG: Ce3+ was synthesized at lower temperature at 1200 °C.•Obtain better morphology precursor and YAG: Ce3+.•Inquiry the effect of the amount of the surfactant to the precursor morphology.Micron-sized Ce-doped yttrium aluminum garnet (YAG: Ce3+) powders are synthesized successfully by a new method including three processes including solvothermal treatment, precursor preheated and annealing treatment in a mild condition. The phase, morphology and luminescent properties are investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), photoluminescence excitation (PLE) and photoluminescence (PL) spectra respectively. The single-phase sample can be formed after solvothermal treatment at 180 °C for 12 h and annealing at 1200 °C for 4 h. The results obtained by SEM show that the particles with narrow size distribution (∼4 μm) and nice morphology are formed after annealing treatment. This indicates that it has good homogeneity and dispersion. The micron-sized Ce-doped YAG shows broad emission bands in the range of 500–680 nm with the maximum intensity at 577 nm.
Co-reporter:Lili Han, Yuhua Wang, Jia Zhang, Ye Tao
Materials Chemistry and Physics 2014 Volume 143(Issue 2) pp:476-479
Publication Date(Web):15 January 2014
DOI:10.1016/j.matchemphys.2013.10.017
•A novel phosphor K2Gd(WO4)(PO4):Tb was successfully synthetized via a solid-state reaction.•The crystal structure of KGWP as a new host matrix was defined.•Visible quantum cutting has been identified in KGWP:0.5Tb3+ system.•CTQE is 183.2% and 176.4% for excitation at 235 and 150 nm.•KGWP:0.5Tb3+ can be a potential candidate for 3D-PDPs and Hg-free lamps.A novel phosphor K2Gd(WO4)(PO4):Tb was prepared via a solid-state reaction. The crystal structure of K2Gd(WO4)(PO4) as a new host matrix for luminescence was defined to be the orthorhombic system with space group Ibca (73). Visible quantum cutting under Tb3+ 4f8–4f75d1 excitation and host excitation in K2Gd(WO4)(PO4):Tb3+ via a downconversion was identified. In order to rationalize the quantum cutting effect, the proper mechanism was proposed. According to calculations, the quantum efficiency was up to 183.2% and 176.4% under excitation at 235 nm and 150 nm, respectively. When compared with Zn2SiO4:Mn2+ (P1-G1S), KGWP:0.5Tb3+ is slightly less bright over 450–650 nm but has a shorter decay time.
Co-reporter:Ge Zhu, Zhipeng Ci, Yurong Shi, Yuhua Wang
Materials Research Bulletin 2014 55() pp: 146-149
Publication Date(Web):
DOI:10.1016/j.materresbull.2014.04.030
Co-reporter:Si Chen, Yuhua Wang, Jia Zhang, Lei Zhao, Qian Wang, Lili Han
Journal of Luminescence 2014 150() pp: 46-49
Publication Date(Web):1 June 2014
DOI:10.1016/j.jlumin.2014.01.021
•The K3R(PO4)2:Tb3+ (R=Y and Gd) can be efficiently excited by VUV light.•The K3R(PO4)2:Tb3+ (R=Y and Gd) show high intensities upon 147 nm excitation.•The K3R(PO4)2:Tb3+ (R=Y and Gd) exhibit strong CL intensities.•The K3R(PO4)2:Tb3+ could be potential candidates for displays and lightings.K3R(PO4)2:Tb3+ (R=Gd and Y) phosphors were prepared by a solid-state reaction method, and their photoluminescence (PL) and cathodoluminescence (CL) properties were investigated. The excitation in vacuum ultraviolet (VUV) region of K3Gd0.3(PO4)2:0.7Tb3+ and K3Y0.3(PO4)2:0.7Tb3+ show broad bands in 125–238 nm, which can match the VUV light sources of 147 and 172 nm for plasma display panels and Hg-free lamps. The 4f–4f5d spin-allowed and spin-forbidden transitions of Tb3+ are verified to be located around 233 and 264 nm, respectively. Both series of phosphors exhibit strong green emissions with the predominated peaks at 545 and 544 nm under 147 and 367 nm excitation, respectively, corresponding to the 5D4→7F5 transition of Tb3+. Under the same conditions, the relative luminance of this phosphor is about 75%, 70% of that of commercial phosphor Zn2SiO4:Mn2+ (ZSM) under 147 nm VUV light, the VUV sensitization of Tb3+ emission by Gd3+ in K3GdY(PO4)2:Tb3+ and the possible VUV luminescence mechanism are investigated. In addition, the CL spectra of K3R(PO4)2:Tb3+ (R=Y and Gd) exhibit Tb3+ characteristic emissions and strong intensities. The above results indicate that K3R(PO4)2:Tb3+ (R=Y and Gd) could be potential candidates as green-emitting VUV and CL phosphors.
Co-reporter:Shaochun Han, Yuhua Wang, Wei Zeng, Wenbo Chen, Gen Li
Journal of Luminescence 2014 152() pp: 66-69
Publication Date(Web):
DOI:10.1016/j.jlumin.2013.10.068
Co-reporter:Wanying Geng, Ge Zhu, Yurong Shi, Yuhua Wang
Journal of Luminescence 2014 155() pp: 205-209
Publication Date(Web):
DOI:10.1016/j.jlumin.2014.06.044
Co-reporter:Ge Zhu, Yurong Shi, Masayoshi Mikami, Yasuo Shimomura, Yuhua Wang
Materials Research Bulletin 2014 50() pp: 405-408
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.11.012
Co-reporter:Ge Zhu, Yuhua Wang, Qian Wang, Xin Ding, Wanying Geng, Yurong Shi
Journal of Luminescence 2014 154() pp: 246-250
Publication Date(Web):
DOI:10.1016/j.jlumin.2014.04.041
Co-reporter:Wei Zeng, Yuhua Wang, Shaochun Han, Wenbo Chen, Gen Li
Journal of Luminescence 2014 152() pp: 210-213
Publication Date(Web):
DOI:10.1016/j.jlumin.2013.10.053
Co-reporter:Jia Zhang, Yuhua Wang, Zhigang Xu, Haixia Zhang, Pengyu Dong, Linna Guo, Fenghua Li, Shuangyu Xin and Wei Zeng
Journal of Materials Chemistry A 2013 vol. 1(Issue 3) pp:330-338
Publication Date(Web):30 Oct 2012
DOI:10.1039/C2TB00045H
In this paper, size-controlled morphologies of (Y, Gd)VO4 and (Y, Gd)VO4:Ln3+ (Ln = Eu, Yb, Er, and Ho) were obtained via a facile hydrothermal route, and their properties for drug delivery and photoluminescence were investigated. Monodisperse ellipsoid-like hollow (Y, Gd)VO4 were designed by employing (Y, Gd)(OH)CO3 colloidal spheres as a sacrificial template and NH4VO3 as a vanadium source, and the formation mechanism could be interpreted by the Kirkendall effect. The control of particle size for hollow (Y, Gd)VO4 was realized, facilitating their practical application. Mesoporous core–shell structured (Y, Gd)VO4:Ln3+@nSiO2@mSiO2 were designed to improve the properties for drug release. Typically, red emission of YVO4:Eu3+ predominated under 465 nm excitation; the upconversion spectra of YVO4:Yb3+, Er3+ and YVO4:Yb3+, Ho3+ revealed green and red color upon 980 nm excitation, respectively. The biocompatibility and drug release evaluations indicate the potential biological applications of the samples.
Co-reporter:Linna Guo, Yuhua Wang, Yanzhao Wang, Jia Zhang, Pengyu Dong and Wei Zeng
Nanoscale 2013 vol. 5(Issue 6) pp:2491-2504
Publication Date(Web):03 Jan 2013
DOI:10.1039/C2NR33577H
A series of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 ≤ x ≤ 12) nanoparticles with average size from 20 to 320 nm upon increasing Li+ concentration were prepared by a coprecipitation method. The detailed crystal structure of Lu6O5F8 as a new matrix is firstly analysed via retrieved refinement of the powder X-ray diffraction (XRD). In addition, the corresponding Powder Diffraction File card information was also obtained through indexing the XRD pattern of the host. Upconversion under excitation at 980 nm, downconversion with Xe lamp as excitation source and cathodoluminescence properties of Lu6O5F8:20%Yb3+,1%Er3+(Tm3+),x%Li+ (0 ≤ x ≤ 12) nanoparticles were compared and studied. It is worthwhile pointing out that according to the effects of Li+ on emission intensity ratio, white UC emission was achieved in the Lu6O5F8:6%Yb3+,0.3%Er3+,0.4%Tm3+,5%Li+ compared to Li+ free sample with the same activator concentration. The reasons behind this behavior were presented and discussed. All in all, Li+ ion would be a wonderful luminescence intensifier for lanthanide ions, and the multifunctional lanthanide ion-doped Lu6O5F8 nanoparticles have potential application in photoluminescence areas and field emission display devices.
Co-reporter:Ge Zhu, Zhipeng Ci, Qian Wang, Yan Wen, Shaochun Han, Yurong Shi, Shuangyu Xin and Yuhua Wang
Journal of Materials Chemistry A 2013 vol. 1(Issue 29) pp:4490-4496
Publication Date(Web):13 May 2013
DOI:10.1039/C3TC30601A
A simple but effective strategy was introduced to realize color tunability of a composite phosphor Y2SiO5:Ce/Y3Al5O12:Ce (YSO:Ce/YAG:Ce). The main idea was to use the cathodoluminescence of the YSO:Ce phosphor to additionally pump the photoluminescence of the YAG:Ce phosphor based on radiative energy transfer. Morphology as well as the cathodoluminescence properties of the YSO:Ce/YAG:Ce phosphors were investigated in detail. According to radiative energy transfer, an intense yellow emission with excellent cathodoluminescence properties can be obtained from YSO:Ce/YAG:Ce phosphors under low voltage electron beam excitation. Moreover, the emission color of the composite phosphors can be tuned from yellow to blue through adjusting the YSO:Ce content. The mechanism for the enhanced yellow emission and the color tunability were also discussed. It was experimentally proved that the color gamut and display hue could be greatly enriched and enhanced when employing the YSO:Ce/YAG:Ce composite phosphor as an additional phosphor for the typical tricolor FED phosphors.
Co-reporter:Wei Zeng, Yuhua Wang, Shaochun Han, Wenbo Chen, Gen Li, Yanzhao Wang and Yan Wen
Journal of Materials Chemistry A 2013 vol. 1(Issue 17) pp:3004-3011
Publication Date(Web):12 Mar 2013
DOI:10.1039/C3TC30182F
A novel yellow emitting long-persistent phosphor Ca2BO3Cl:Eu2+,Dy3+ is developed. The incorporation of Dy3+ ions, which act as trap centers, largely extends the thermoluminescence characteristics and evidently enhances the persistent luminescence behavior of the phosphor. Both fluorescence and phosphorescence spectra of Ca2BO3Cl:Eu2+,Dy3+ reveal only one asymmetric broad emission band located at 580 nm, ascribed to the 5d–4f transitions of Eu2+ ions in two different sites. With the optimum doping concentration and sufficient excitation with UV light, the afterglow of samples can persist over 48 h above the recognizable intensity level (≥0.32 mcd m−2), a phenomenon that is infrequent and excellent. Furthermore, Ca2BO3Cl possesses an indirect bandgap of about 5.1 eV. Detailed processes and possible mechanism are studied and discussed.
Co-reporter:Pengyu Dong, Yuhua Wang, Huihui Li, Hao Li, Xinlong Ma and Lili Han
Journal of Materials Chemistry A 2013 vol. 1(Issue 15) pp:4651-4656
Publication Date(Web):20 Feb 2013
DOI:10.1039/C3TA00130J
A novel and facile soft-chemical method has been proposed for the synthesis of Ag3PO4 crystals with various new morphologies (branch, tetrapod, nanorod, triangular prism), and the morphological effect on the photocatalytic activity of the obtained Ag3PO4 crystals has been investigated. It is demonstrated that the morphology of Ag3PO4 crystals can be controlled by simply adjusting external experimental conditions such as static and ultrasonic conditions. Photocatalytic results indicate that the branched Ag3PO4 crystal with porous structure shows the highest photocatalytic activity among these Ag3PO4 crystals with multiform morphologies, and the photocatalytic rate constants of branched Ag3PO4 are 2.8 and 4 times those of irregular spherical Ag3PO4 for degradation of methylene blue (MB) and rhodamine B (RhB) dye solutions under visible light irradiation, respectively.
Co-reporter:Linna Guo, Yuhua Wang, Lili Han, Qinping Qiang, Wei Zeng, Zehua Zou, Bing Wang and Xiaoxia Guo
Journal of Materials Chemistry A 2013 vol. 1(Issue 47) pp:7952-7962
Publication Date(Web):17 Oct 2013
DOI:10.1039/C3TC31838A
In the present paper, the band structure and density of states of Lu6O5F8 were primarily studied with the help of first-principles calculations, and the indirect band gap of Lu6O5F8 is estimated to be 4.13 eV wide. Lu(OH)1.57F1.43/NH4Lu2F7/Lu6O5F8 nano/microcrystals with diverse morphologies, sizes and dimensions have been synthesized via a mild and controllable hydrothermal process using citric acid trisodium salt dehydrate (Cit3−), hexadecyltrimethylammonium bromide (CTAB), ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid disodium salt (EDTA2−), sodium dodecyl benzene sulfonate (SDBS), ethylenediamine (EA) or polyvinylpyrrolidone (PVP), etc. as an additive, respectively. The phases, morphologies, sizes, and luminescence properties of the as-prepared samples were well characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) and cathodoluminescence (CL) spectroscopy, respectively. The results indicate that the phase, morphology, and size of Lu(OH)1.57F1.43/Lu6O5F8 can be tuned in a controlled manner by altering the amount or kinds of additives, the pH values of the initial solution, and the reaction time. Furthermore, the time-dependent morphology evolution shows that the resulting microrods, hexagonal prisms, flower clusters and spheres were synthesized by a dissolution–reconstruction formation mechanism. It is expected that the synthetic strategy can be extended to controllable synthesis of other types of nano/microcrystals as well. Upon ultraviolet (UV), vacuum ultraviolet (VUV) and electron beam excitation, the luminescence properties as well as the emission mechanisms of the Ln3+ (Ln = Eu/Tb/Ce/Dy) single doped precursor (NH4Lu2F7, Lu(OH)1.57F1.43) and final product (Lu6O5F8) are all compared and studied. All in all, the multifunctional Ln3+ doped NH4Lu2F7/Lu(OH)1.57F1.43/Lu6O5F8 nano/microcrystals have potential applications in photoluminescence areas and field emission display devices.
Co-reporter:Zhengyan Zhao, Zhigang Yang, Yurong Shi, Chuang Wang, Bitao Liu, Ge Zhu and Yuhua Wang
Journal of Materials Chemistry A 2013 vol. 1(Issue 7) pp:1407-1412
Publication Date(Web):07 Jan 2013
DOI:10.1039/C2TC00732K
A novel red-emitting oxonitridosilicate phosphors, Sr2SiNzO4−1.5z:Eu2+ (0.7 < z < 1.2), was prepared by solid state reaction in NH3–N2 atmosphere. The crystal structure was determined by Rietveld analysis on powder X-ray data. Sr2SiNzO4−1.5z (0.7 < z < 1.2) crystallizes in an orthorhombic structure with the space group of Pmnb: ba−c (no. 62), and cell parameter a = 5.67366(5) Å, b = 7.09777(4) Å, c = 9.75112(1) Å. Sr2SiNzO4−1.5z:Eu2+ (0.7 < z < 1.2) exhibited broad-band red emission centred at ∼620 nm (FWHM ≈ 95 nm) under blue light irradiation with a high QE value of 78.0% and good thermal stability, its emission intensity remains 87% at 150 °C of that measured at room temperature. The outstanding luminescent properties allow it to be an attractive red luminescent material for white LEDs.
Co-reporter:Shuangyu Xin, Yuhua Wang, Pengyu Dong, Wei Zeng and Jia Zhang
Journal of Materials Chemistry A 2013 vol. 1(Issue 48) pp:8156-8160
Publication Date(Web):23 Oct 2013
DOI:10.1039/C3TC31356E
CaAl2O4:Eu2+, Nd3+ nanofibers were prepared via the electrospinning process by using core–sheath CaAl2O4:Eu2+, Nd3+/carbon nanofibers as templates, combined with a subsequent annealing treatment. The obtained nanofibers are smooth with tunable diameters ranging from 50 to 120 nm by simply changing the ratio of inorganic precursors to solvent. The intermediate state is composed of hollow CaAl2O4:Eu2+, Nd3+@carbon nanofibers. The formation process, luminescent properties and long lasting performance are investigated. This facile method for synthesizing nanofibers may have potential applications in the field of in vivo imaging and coatings for long lasting phosphors.
Co-reporter:Yan Wen, Bitao Liu, Wei Zeng and Yuhua Wang
Nanoscale 2013 vol. 5(Issue 20) pp:9739-9746
Publication Date(Web):30 Jul 2013
DOI:10.1039/C3NR03024E
Anatase/rutile mixed titania nanotubes (TiO2 NTs) precipitated with gold nanoparticles (Au NPs), i.e. Au/TiO2, have been synthesized and investigated on visible photocatalysis properties. A deposition–precipitation (DP) method was adopted to reduce the gold precursor to Au NPs within the preformed TiO2 NTs by the emulsion electrospinning technique. The optimal visible photocatalytic activity was found in the sample Au3(DP350)/TiO2 with a loading of 3 wt% Au NPs and calcining at 350 °C. Through transmission electron microscopy, Au NPs of 4.16 nm diameter were observed at the interface between the anatase and rutile phases in the optimal Au3(DP350)/TiO2 sample, and these joint active sites at the interface were beneficial for charge separation. The obtained optimal photocatalytic efficiency of Au3(DP350)/TiO2 was ascribed to the synergistic effect of the enhanced visible absorption and the anatase/rutile mixed-phase composition, and the possible mechanism for this was discussed in detail.
Co-reporter:Linna Guo, Yuhua Wang, Wei Zeng, Lei Zhao and Lili Han
Physical Chemistry Chemical Physics 2013 vol. 15(Issue 34) pp:14295-14302
Publication Date(Web):25 Jun 2013
DOI:10.1039/C3CP51816G
A series of GdF3:Yb3+, Ln3+ (Ln = Ho, Tm, Er, Pr, Tb) nanoparticles were prepared by a simple and green hydrothermal method without any additives, which exhibited an ellipse-like shape with a diameter of 63 nm and a length of 101 nm on average. To prove the existence (or not) of near infrared quantum cutting for various lanthanide ion couples (Yb/Ho; Yb/Tm; Yb/Er; Yb/Pr; Yb/Tb) in one host lattice (GdF3), the measured luminescence spectra and decay lifetimes of these samples were analysed. Furthermore, the band structures and densities of state of GdF3 were also studied with the help of first-principles calculations, and the direct band gap of GdF3 was estimated to be 7.443 eV wide. Based on this, detailed processes and possible mechanisms of the luminescence phenomena are discussed. GdF3:Yb3+, Ln3+ nanoparticles may have potential applications in modifying the solar spectrum to enhance the efficiency of silicon solar cells.
Co-reporter:Jia Zhang, Yuhua Wang, Linna Guo and Pengyu Dong
Dalton Transactions 2013 vol. 42(Issue 10) pp:3542-3551
Publication Date(Web):28 Nov 2012
DOI:10.1039/C2DT32463F
Monodisperse and uniform Y6O5F8:RE3+ (RE = Yb, Er, and Ho) microarchitectures with various morphologies have been constructed by a facile surfactant-assisted hydrothermal route, and their up-conversion luminescence and NIR quantum cutting properties were investigated. Hollow hexagonal prisms, microbundle gatherings by rods, and solid hexagonal prisms were designed by employing CTAB, PVP, and EDTA as additives, respectively. Under 980 nm excitation, the Y5.34O5F8:0.6Yb3+, 0.06Er3+ samples obtained using different additives exhibit similar emission spectra profiles with predominating peaks at 670 nm; the Y5.34O5F8:0.6Yb3+, 0.06Ho3+ samples give green emissions with the strongest peaks around 544 nm. The NIR quantum cutting for the Y6O5F8:Yb3+, Ho3+ samples was identified by the NIR emission spectra upon both 360 and 450 nm excitation. The corresponding quantum cutting mechanisms were discussed through the energy level diagrams, in which a back-energy-transfer from Yb3+ to Ho3+ was first proposed to interpret the spectral characteristics. A modified calculation equation for the quantum efficiency of Yb3+–Ho3+ coupled by exciting at 450 nm was suggested according to the quantum cutting mechanism. The efficient NIR luminescence and quantum cutting in Yb3+, Ho3+ co-doped Y6O5F8 reveal a possible application in modifying the solar spectrum to enhance the efficiency of silicon solar cells.
Co-reporter:Meidan Que, Zhipeng Ci, Yuhua Wang, Ge Zhu, Shuangyu Xin, Yurong Shi and Qian Wang
CrystEngComm 2013 vol. 15(Issue 32) pp:6389-6394
Publication Date(Web):31 May 2013
DOI:10.1039/C3CE40482J
Europium-doped apatite Ca10(SiO4)3(SO4)3F2 (CSSF) has been successfully synthesized by solid state reaction. The crystal structure of CSSF:0.006Eu2+ is refined by the Maud refinement method. Optical properties of the prepared samples are found to depend on the rare-earth metal–oxygen distances and lattice iconicity. The excitation spectra of the CSSF:Eu2+ phosphors centered at 350 nm and covered the range from 250 to 450 nm. Under 350 nm excitation, the emission spectra of CSSF:Eu2+ phosphors show a blue (centered at 420 nm) and a green (centered at 525 nm) emission band, respectively. Meanwhile, the concentration quenching and energy transfer mechanism have been investigated via the configuration coordinate diagram. The key parameters, such as the temperature-dependent photoluminescence and CIE values of the CSSF:Eu2+ phosphor have also been studied.
Co-reporter:Lili Han, Yuhua Wang, Yanzhao Wang, Jia Zhang, Ye Tao
Journal of Alloys and Compounds 2013 Volume 551() pp:485-489
Publication Date(Web):25 February 2013
DOI:10.1016/j.jallcom.2012.11.011
Undoped and Tb3+-doped borates KBaY(BO3)2 phosphors were synthesized through the conventional high-temperature solid state method and their photoluminescence properties under vacuum ultraviolet excitation were evaluated. Upon 172 nm excitation, KBaY(BO3)2 exhibits an intrinsic broad ultraviolet emission centered at 328 nm attributed to the BO33- group. When Tb3+ was introduced into KBaY(BO3)2, an efficient energy transfer from the host to Tb3+ was observed which had been well proved by spectra and decay time. The optimal sample of KBaY(BO3)2:0.1Tb3+ shows a stronger absorption at 172 nm, a comparable brightness and a shorter decay time compared with those of the commercial Zn2SiO4:Mn2+. These results demonstrate that KBaY(BO3)2:0.1Tb3+ could be a promising green-emitting phosphor for three-dimensional plasma display panel.Highlights► KBYB exhibits an intrinsic broad UV emission under 172 nm excitation. ► Energy transfer from host to Tb3+ in KBYB is studied in detail. ► The host-Tb3+ ET can be proved by PL spectra and decay time. ► KBYB:Tb3+ shows good luminescence properties under VUV excitation. ► KBYB:Tb3+could be used as a potential candidate for PDPs.
Co-reporter:Ge Zhu, Shuangyu Xin, Yan Wen, Qian Wang, Meidan Que and Yuhua Wang
RSC Advances 2013 vol. 3(Issue 24) pp:9311-9318
Publication Date(Web):03 Apr 2013
DOI:10.1039/C3RA00040K
A novel single phased white light emitting phosphor Sr10[(PO4)5.5(BO4)0.5](BO2):Eu2+, Mn2+, Tb3+ was synthesized by solid-state reaction for the first time. The crystal structure, photoluminescence properties and the efficient energy transfer from different Eu2+ sites to Mn2+ and Tb3+ in Sr10[(PO4)5.5(BO4)0.5](BO2) is studied in detail by X-ray diffractometry Rietveld method, luminescence spectra, energy-transfer efficiency and lifetimes. Through effective energy transfer, the wavelength-tunable warm white light can be realized with superior chromaticity coordinates of (0.37, 0.30) and low correlated color temperature (CCT = 3512 K) by coupling the emission bands peaking at 410, 542 and 649 nm attributed to the contribution from Eu2+, Tb3+ and Mn2+, respectively. The results indicate the white phosphor Sr10[(PO4)5.5(BO4)0.5](BO2):Eu2+, Mn2+, Tb3+ can serve as a promising material for phosphor-converted warm white LEDs.
Co-reporter:Yuhua Wang, Yu Gong, Xuhui Xu, Yanqin Li
Journal of Luminescence 2013 Volume 133() pp:25-29
Publication Date(Web):January 2013
DOI:10.1016/j.jlumin.2011.12.046
This paper highlights work from our laboratory on the recent progress in green, orange-yellow, and red long persistent phosphors. In addition, the phosphorescence mechanism in Eu2+-containing phosphors is also discussed.Highlights► A new orange-yellow long persistent phosphor Sr3Al2O5Cl2:Eu2+, Tm3+ was found. ► A new red long persistent phosphor Sr2SnO4:Sm3+ was found. ► A novel silicate long persistent phosphor was found. ► The photoionization of Eu2+ to Eu3+ was found in BaMgSiO4.
Co-reporter:Meidan Que, Zhipeng Ci, Yuhua Wang, Ge Zhu, Yurong Shi, Shuangyu Xin
Journal of Luminescence 2013 Volume 144() pp:64-68
Publication Date(Web):December 2013
DOI:10.1016/j.jlumin.2013.06.052
•A new Ca2La8(GeO4)6O2 (CLGO) compound has been synthesized for the first time.•The crystal structure of CLGO has been refined by Maud refinement method.•Photoluminescence spectra of CLGO:RE3+ were firstly investigated.A new Ca2La8(GeO4)6O2 (CLGO) compound has been synthesized via solid-state reaction process for the first time. The crystal structure of CLGO was refined and determined by Maud Program. The photoluminescence spectra (PL), cathodoluminescence spectra (CL), and lifetimes as well as temperature dependence of photoluminescence of CLGO:RE3+ (RE3+=Eu3+, Tb3+, Dy3+, Sm3+, Tm3+) were investigated in detail. Under the excitation of ultraviolet, CLGO:RE3+ (RE3+=Eu3+, Tb3+, Dy3+, Sm3+, Tm3+) show red, green, yellow, orange, violet emission, respectively.
Co-reporter:Yao Li, Hairong Li, Bitao Liu, Jia Zhang, Zhengyan Zhao, Zhigang Yang, Yan Wen, Yuhua Wang
Journal of Physics and Chemistry of Solids 2013 Volume 74(Issue 2) pp:175-180
Publication Date(Web):February 2013
DOI:10.1016/j.jpcs.2012.09.020
A series of white-light-emitting NaSrPO4:Eu2+, Mn2+ phosphors were successfully synthesized by solid-state reaction and their photoluminescence properties were investigated. The NaSrPO4:Eu2+, Mn2+ phosphor system exhibits a broad excitation band in the wavelength range of 250–420 nm, which is well-matched with ultraviolet (UV) light-emitting-diode (LED) chips (typically 365 nm). As a result of fine-tuning of the emission composition of the Eu2+ and Mn2+ ions, warm-white-light emission can be realized in a single host lattice under 365 nm excitation. Efficient resonant energy transfer from the Eu2+ to Mn2+ ions has been observed. The energy transfer efficiency and critical distance were calculated. The results indicate that the developed phosphor can be used as a potential candidate for white LEDs.
Co-reporter:Zhigang Yang, Zhengyan Zhao, Meidan Que, Yuhua Wang
Optical Materials 2013 Volume 35(Issue 7) pp:1348-1351
Publication Date(Web):May 2013
DOI:10.1016/j.optmat.2013.01.024
Rare-earth-doped β-SiAlON phosphors, with the compositions of Si6−zAlzOzN8−z:xRe (z = 1, Re = Sm or Dy, 0.01 ⩽ x ⩽ 0.05), were prepared by a solid-state reaction at high temperature. The photoluminescence properties were investigated as functions of the rare earths (i.e., x) concentration. In β-SiAlON:Sm2+, broad 4f55d1 → 4f6 emission and line 5D0 → 7FJ emission were observed at room temperature. The characteristic 4F9/2 → 6H15/2 (blue) and 4F9/2 → 6H13/2 (yellow) transitions of Dy3+ were detected in the emission spectra. And the thermal quenching properties of β-SiAlON:Sm2+ and β-SiAlON:Dy3+ were investigated.Highlights► β-SiAlON:Sm/Dy phosphors have been prepared at 1600 °C under atmospheric pressure. ► Photoluminescence and thermal stability have been investigated. ► They could be used as a potential candidate for UV LEDs.
Co-reporter:Lili Han, Yuhua Wang, Jia Zhang, Yanzhao Wang
Materials Chemistry and Physics 2013 Volume 139(Issue 1) pp:87-91
Publication Date(Web):15 April 2013
DOI:10.1016/j.matchemphys.2012.12.048
The present investigation aims at the luminescence properties of Ca9Y(VO4)7:Eu3+, Bi3+ red phosphor materials. The red emission at 613 nm originating from 5D0–7F2 transition of Eu3+ in Ca9Y(VO4)7 is enhanced strongly with Bi3+–V5+ couple as the sensitizer, under excitation either into the 5L6 state or the 5D2 state. The energy transfer from Bi3+–V5+ to Eu3+ is discussed. For a fixed Eu3+ concentration, there is an optimal Bi3+ concentration with 15 mol%, at which the maximum luminescence intensity of Eu3+ is achieved. The red emission of Ca9Y(VO4)7:0.8Eu3+, 0.15Bi3+ (under 395 nm and 465 nm excitations) is stronger than that of commercial Y2O3:Eu3+ phosphor (under 395 nm and 467 nm excitations). Based on the ratios of the red emission at 613 nm to orange one at 592 nm, it is considered that the symmetry of Eu3+ site decreases with doping of Bi3+, leading to more opposite parity components. Lifetime and diffuse reflection spectra measurements indicate that the red emission enhancement is due to the enhanced transition probabilities from the ground state to 5L6 and 5D2 states of Eu3+ in the distorted crystal field. Therefore the present material is a promising red-emitting phosphor for white-light diodes with near-ultraviolet/blue GaN-based chips.Highlights► Ca9Y(VO4)7:0.15Bi3+, 0.8Eu3+ (excited at 395/465 nm) has a stronger brightness than Y2O3:Eu3+ (excited at 395/467 nm). ► The energy transfer from Bi3+–V5+ to Eu3+ is discussed. ► Based on the R/O value, the symmetry of Eu3+ site decreases with doping of Bi3+. ► The present material can be potentially used for LEDs with near-UV/blue GaN-based chips.
Co-reporter:Wenjing Liu, Yuhua Wang, Mingqi Zhang, Yunxian Zheng
Materials Letters 2013 Volume 96() pp:42-44
Publication Date(Web):1 April 2013
DOI:10.1016/j.matlet.2012.12.104
Y2O3:Eu3+ is an excellent red-emitting phosphor which has been widely used for display and lighting devices. However the production cost is high due to the high concentration of the expensive Eu activator. In order to reduce the producing cost, Y2O3:Eu3+ coated Y2O3 particles are prepared by urea-assisted homogeneous precipitation. The synthesis process involves dispersing of Y2O3 particles in a reacting medium, precipitating (Y,Eu)(OH)CO3 on the surface of Y2O3 particles through homogeneous precipitation of Y3+ and Eu3+ using urea as the precipitator, and transferring (Y,Eu)(OH)CO3 to Y2O3:Eu3+ by annealing at 900 °C for 3 h. Scanning electron microscopy (SEM) images and photoluminescence spectra (PL) indicate that Y2O3:Eu3+ coated Y2O3 particles with good luminescence property are synthesized successfully.Highlights► Y2O3:Eu3+ coated Y2O3 particles were prepared by urea-assisted homogeneous precipitation. ► The morphology of (Y,Eu)(OH)CO3 was related with reacting time and concentration of initial reagent. ► The experimental condition as B3 sample was chosen to coat Y2O3 particles with (Y,Eu)(OH)CO3 precursor.
Co-reporter:Ge ZHU, Zhipeng CI, Yurong SHI, Yuhua WANG
Journal of Rare Earths 2013 Volume 31(Issue 11) pp:1049-1052
Publication Date(Web):November 2013
DOI:10.1016/S1002-0721(12)60401-3
Rare earth Sm3+, Pr3+ doped NaSr2(NbO3)5 red phosphors were successfully synthesized. X-ray diffraction analysis indicated that all the samples were single phased. The luminescence property was investigated in detail by diffuse-reflectance spectra and photoluminescence spectra measurement. Both NaSr2(NbO3)5:Sm3+ and NaSr2(NbO3)5:Pr3+ phosphors showed strong absorption in near ultraviolet region, which was suitable for application in LEDs. When excited by UV light, they both emitted bright red emission with CIE chromaticity coordinates (0.603, 0.397) and (0.669, 0.330), respectively. The optimal doping concentration of Sm3+ doped NaSr2(NbO3)5 was measured to be 0.04 and that for Pr3+ doped NaSr2(NbO3)5 was 0.01. The integral emission intensity was also measured and compared with the commercial red phosphor Y2O3:Eu3+. The results indicated that NaSr2(NbO3)5:RE3+ (RE=Sm, Pr) have potential to serve as a red phosphor for UV pumped white LEDs.CIE chromaticity coordinates of NSN:0.04Sm3+, NSN:0.01Pr3+ and the commercial Y2O3:Eu3+
Co-reporter:Ge Zhu, Zhipeng Ci, Shuangyu Xin, Yan Wen, Yuhua Wang
Materials Letters 2013 Volume 91() pp:304-306
Publication Date(Web):15 January 2013
DOI:10.1016/j.matlet.2012.09.072
Dy3+ doped NaSr2Nb5O15 series were firstly synthesized by solid-state reaction method. Crystal structure and characteristic luminescence properties are investigated in detail by X-ray diffraction refinement and photoluminescence spectra measurement. NaSr2Nb5O15:Dy3+ exhibits strong absorption in near ultraviolet–blue region and intense warm white emission with CIE chromaticity coordinates (0.396, 0.433) and low correlated color temperature (3970 K) upon 388 nm excitation. The warm white LED has also been fabricated by combining with GaN (365–370 nm chip) and single NaSr2Nb5O15:Dy3+ phosphor. The results show that NaSr2Nb5O15:Dy3+ could be a promising phosphor for warm white LEDs.Highlights► A new phosphor NaSr2Nb5O15:Dy3+ was synthesized and investigated firstly. ► Crystal structure and characteristic luminescence properties are discussed. ► It can exhibit warm white emission with CIE (0.396, 0.433) and low CCT (3970 K). ► The warm white emitting LED has also been fabricated.
Co-reporter:Zhigang Yang, Zhengyan Zhao, Bitao Liu, Yuhua Wang
Materials Letters 2013 Volume 93() pp:32-35
Publication Date(Web):15 February 2013
DOI:10.1016/j.matlet.2012.11.071
β-SiAlON:Ln3+ (Ln=Yb/Ho, Yb/Er) microparticles with up-conversion (UC) luminescence properties were successfully synthesized via a solid-state reaction method by employing Si3N4 (nanopowder), Al2O3 (nanopowder) and rear-earth oxides. The results show that the β-SiAlON:Ln3+ microparticles have a size ranging from 100 to 400 nm. Under the 980 nm NIR laser excitation, Yb/Er and Yb/Ho codoped samples exhibit UC luminescence centered at 658 and 660 nm, respectively. The power dependency and the dynamics of the UC luminescence confirm the existence of two-photon UC processes in Yb/Er and Yb/Ho codoped samples respectively, and the UC mechanisms were given.Highlights► β-SiAlON:Ln3+ (Ln=Yb/Ho, Yb/Er) have been prepared at 1600 °C. ► The results show pure phase, well-crystallized and -dispersed. ► They could be a new complement for UC luminescence.
Co-reporter:Yurong Shi, Ge Zhu, Masayoshi Mikami, Yasuo Shimomura, Yuhua Wang
Materials Research Bulletin 2013 48(1) pp: 114-117
Publication Date(Web):
DOI:10.1016/j.materresbull.2012.10.014
Co-reporter:Zhigang Yang, Zhengyan Zhao, Yurong Shi, Yuhua Wang
Materials Research Bulletin 2013 48(10) pp: 4048-4050
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.06.033
Co-reporter:Ge Zhu, Zhipeng Ci, Chaoyang Ma, Yurong Shi, Yuhua Wang
Materials Research Bulletin 2013 48(5) pp: 1995-1998
Publication Date(Web):
DOI:10.1016/j.materresbull.2012.12.074
Co-reporter:Shuangyu Xin, Yuhua Wang, Ge Zhu, Feng Zhang, Yu Gong, Yan Wen, Bitao Liu
Materials Research Bulletin 2013 48(4) pp: 1627-1631
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.01.008
Co-reporter:Qian Wang, Zhipeng Ci, Yuhua Wang, Ge Zhu, Yan Wen, Yurong Shi
Materials Research Bulletin 2013 48(3) pp: 1065-1070
Publication Date(Web):
DOI:10.1016/j.materresbull.2012.11.114
Co-reporter:Lili Han, Yuhua Wang, Lei Zhao, Jia Zhang, Yanzhao Wang, Ye Tao
Materials Research Bulletin 2013 48(6) pp: 2139-2142
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.02.030
Co-reporter:Pengyu Dong, Yuhua Wang, Linna Guo, Bin Liu, Shuangyu Xin, Jia Zhang, Yurong Shi, Wei Zeng and Shu Yin
Nanoscale 2012 vol. 4(Issue 15) pp:4641-4649
Publication Date(Web):13 Jun 2012
DOI:10.1039/C2NR31231J
Graphene sheets were obtained through solvothermal reduction of colloidal dispersion of graphene oxide in benzyl alcohol. The graphene/rod-shaped TiO2 nanocomposite was synthesized by this novel and facile solvothermal method. During the solvothermal reaction, both the reduction of graphene oxide and the growth of rod-shaped TiO2 nanocrystals as well as its deposition on graphene occur simultaneously. The photocatalytic activity of graphene/rod-shaped TiO2 and graphene/spherical TiO2 nanocomposites was compared. In the photocatalytic degradation of methyl orange (MO), the graphene/rod-shaped TiO2 nanocomposite with the optimized graphene content of 0.48 wt% shows good stability and exhibits a significant enhancement of photocatalytic activity compared to the bare commercial TiO2 (P25) and graphene/spherical TiO2 nanocomposite with the same graphene content. Photocurrent experiments were performed, which demonstrate that the photocurrent of the graphene/rod-shaped TiO2 nanocomposite electrode is about 1.2 times as high as that of the graphene/spherical TiO2 nanocomposite electrode. The photocatalytic mechanism of graphene/rod-shaped TiO2 nanocomposite was also discussed on the basis of the experimental results. This work is anticipated to open a possibility in the integration of graphene and TiO2 with various morphologies for obtaining high-performance photocatalysts in addressing environmental protection issues.
Co-reporter:Bitao Liu, Yongji Huang, Yan Wen, Luojun Du, Wei Zeng, Yurong Shi, Feng Zhang, Ge Zhu, Xuhui Xu and Yuhua Wang
Journal of Materials Chemistry A 2012 vol. 22(Issue 15) pp:7484-7491
Publication Date(Web):2012/03/09
DOI:10.1039/C2JM16114A
A series of composites of nanocrystalline TiO2 with exposed {001} facets and high quality graphene sheets (GS) were synthesized via a one-step hydrothermal reaction in an ethanol–water solvent. The obtained {001} facets-exposed TiO2/GS photocatalysts were characterized by Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction pattern (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet visible (UV-vis) diffuse reflectance spectroscopy (DRS) and Electrical Impedance Spectroscopy (EIS). They showed a better photocatalyst properties than P25 and other normal TiO2/GS composites, which could be explained on the basis of the formation of chemical Ti–O–C bond and the formation of nano-sized Schottky interfaces at the contacts between TiO2 and GS. The influence of the exposed {001} facets on the photocatalytic activity was investigated. The result showed that positively charged dye molecules are preferentially adsorbed onto the TiO2/GS composites due to the photogenerated charge gathered on GS. Overall, this work could provide new insights into the fabrication of TiO2–carbon composites as high performance photocatalysts and facilitate their application in addressing environmental protection issues.
Co-reporter:Linna Guo, Yanzhao Wang, Yuhua Wang, Jia Zhang and Pengyu Dong
CrystEngComm 2012 vol. 14(Issue 9) pp:3131-3141
Publication Date(Web):27 Feb 2012
DOI:10.1039/C2CE06616E
A series of Yb3+, Ho3+ codoped BaGdF5 with different morphologies (nanoparticles, peanut-like and capsule-like submicrocrystals) and sizes (37–900 nm) are prepared by a facile additive-assisted hydrothermal route. The crystal structure of BaGdF5 solid-solution is firstly established via the materials studio software and retrieved refinement of the powder XRD data. In addition, upconversion and downconversion luminescence properties of Yb3+, Ho3+ codoped BaGdF5 samples are studied, and the energy transfer (Yb3+ → Ho3+) efficiency of the sample with the strongest UC emission is also calculated. The measured field dependence of magnetization of the Yb3+, Ho3+ codoped BaGdF5 nanoparticles shows excellent paramagnetism. The above results show that versatile lanthanide nanoparticles with these properties combined in a single particle are of considerable importance in biomedical luminescence applications. The Raman spectrum of the BaGdF5 host is presented here, and the low phonon energy is mainly respond for the high UC and DC efficiency of the product.
Co-reporter:Yurong Shi, Yuhua Wang, Dan Wang, Bitao Liu, Yanhui Li, and Lan Wei
Crystal Growth & Design 2012 Volume 12(Issue 4) pp:1785-1791
Publication Date(Web):February 29, 2012
DOI:10.1021/cg201225k
Hexagonal prism (La, Ce, Tb)PO4 green phosphors have been successfully prepared via a precipitation method route at ambient pressure from aqueous solution. The precipitation was obtained from lanthanide-nitrate complexes and (NH4)2HPO4 with citric acid as a structural modifier. The prism length diameter ratio and size can be tailored by varying the content of citric acid and the acidity of the solution, respectively. The mechanism of how the citric acid and acidity affect morphology has also been studied. Scanning electron microscopy, transmission electron microscopy, high-resolution transmission electron microscopy, X-ray diffraction, and differential thermal analysis-thermogravimetry were used to characterize the morphology of the products and investigate the possible mechanism of formation and growth of the hexagonal prism. Furthermore, photoluminescence (PL) properties of (La, Ce, Tb)PO4 products were also carried out and compared with those of commercial phosphors.
Co-reporter:Zhengyan Zhao, Yuhua Wang
Journal of Luminescence 2012 Volume 132(Issue 11) pp:2842-2846
Publication Date(Web):November 2012
DOI:10.1016/j.jlumin.2012.05.038
A novel ZrO2:Sm3+,Sn4+ phosphor is synthesized by solid state reaction. The ZrO2:Sm3+ does not show afterglow. But, after doping Sn4+, intense red afterglow luminescence is firstly observed in ZrO2:Sm3+,Sn4+ and it can last more than 1000 s at maximum. The afterglow decay curves of ZrO2:Sm3+,Sn4+ are fitted by three exponential components and the decay process consists of initial fast, intermediate and slow decay. The thermoluminescence indicates that the Sn4+ ions induce suitable traps with the depth of 0.436 eV and result in efficient afterglow luminescence of ZrO2:Sm3+,Sn4+. The thermoluminescence filling and fading experiments further confirm the important role of the proper shallow traps induced by doping Sn4+ on the afterglow of ZrO2:Sm3+,Sn4+.Highlights► We obtain a novel red afterglow phosphor ZrO2:Sm3+,Sn4+. ► The important role of Sn4+ on the afterglow is investigated. ► We give a feasible interpretation for the occurrence of afterglow in ZrO2:Sm3+,Sn4+.
Co-reporter:Ge Zhu, Yuhua Wang, Zhipeng Ci, Bitao Liu, Yurong Shi, Shuangyu Xin
Journal of Luminescence 2012 Volume 132(Issue 2) pp:531-536
Publication Date(Web):February 2012
DOI:10.1016/j.jlumin.2011.09.029
A single-phased white-light-emitting phosphor Ca8Mg(SiO4)4Cl2:Ce3+, Tb3+ (CMSC:Ce3+, Tb3+) is synthesized by a high temperature solid-state reaction method, and its photoluminescence properties are investigated. The obtained phosphor exhibits a strong excitation band between 250 and 410 nm, matching well with the dominant emission band of a UV light-emitting-diode (LED) chip. Energy transfer from Ce3+ to Tb3+ ions has been investigated and demonstrated to be a resonant type via a dipole–dipole mechanism. The energy transfer efficiency as well as the critical distance is also estimated. Furthermore, the phosphors can generate light from yellow-green through white and eventually to blue by properly tuning the relative ratio of Ce3+ to Tb3+ ions grounded on the principle of energy transfer. The results show that this phosphor has potential applications as a single-phased phosphor for UV white-light LEDs.Highlights► The luminescence properties of Ca8Mg(SiO4)4Cl2:Ce3+, Tb3+ were investigated for the first time. ► The strong absorption of phosphors matches well with the emission band of UV LED chips. ► The energy transfer from Ce3+ to Tb3+ in Ca8Mg(SiO4)4Cl2 was investigated in detail. ► The white light (CIE=(0.29, 0.34)) is generated by tuning the relative ratio of Ce3+ to Tb3+.
Co-reporter:Pengyu Dong, Yuhua Wang, Bin Liu, Linna Guo, Yongji Huang, Shu Yin
Applied Surface Science 2012 Volume 258(Issue 18) pp:7052-7058
Publication Date(Web):1 July 2012
DOI:10.1016/j.apsusc.2012.03.164
Abstract
The traditional hydrothermal method for synthesis of H2Ti3O7 nanotubes was modified, and the total hydrothermal reaction time of forming a matured network of H2Ti3O7 nanotubes was successfully decreased by 50%. The effect of hydrothermal reaction time on morphology and photocatalytic activity of H2Ti3O7 nanotubes was investigated and discussed. Various morphologies can be observed in the as-prepared samples with different hydrothermal reaction times. The photocatalytic activity of the as-prepared samples was evaluated for degradation of methyl orange (MO) under simulated solar irradiation. It was found that the sample treated in the hydrothermal condition for 36 h with a matured network of H2Ti3O7 nanotubes showed excellent photocatalytic activity. The photocatalytic activity results were discussed in detail. The stronger absorption in the ultraviolet (UV) range, the increasing crystallization of H2Ti3O7 phase, and larger surface area and pore volume contributed to the enhancement of photocatalytic activity of the as-prepared samples.
Co-reporter:Bitao Liu, Yuhua Wang, Yan Wen, Feng Zhang, Ge Zhu, Jia Zhang
Materials Letters 2012 Volume 75() pp:137-139
Publication Date(Web):15 May 2012
DOI:10.1016/j.matlet.2012.02.011
The S-doped BaAl12O19:Mn2+ phosphors were synthesized by an environmentally benign synthesis reaction. Photoluminescence spectra, powder X-ray diffraction, energy dispersion spectrum and decay curves were used to evaluate the S-doped BaAl12O19:Mn2+ phosphors. It reveals that sulfur doping would lead to a sharp increase of 33.8% in luminance intensity and only a slightly longer decay time. This could be due to the decrease of defects traps and more covalent crystal field surrounding Mn2+ when sulfur ions occupied the unstable conduction O sites. The result shows that this environmentally benign synthesis is expected to be potentially applicable to the plasma display panels' industrial production of BaAl12O19:Mn2+ phosphors.Highlights► An environmentally benign synthesis reaction was employed to synthesis BaAl12O19:Mn2+ phosphors. ► An increase of 33.8% in luminance intensity and only a slightly longer decay time can be obtained. ► The structure of BaAl12O19:Mn2+ and lattice defect were discussed in detailed.
Co-reporter:Yan Wen, Yuhua Wang, Bitao Liu, Feng Zhang
Optical Materials 2012 Volume 34(Issue 5) pp:889-892
Publication Date(Web):March 2012
DOI:10.1016/j.optmat.2011.12.005
The vacuum ultraviolet excited luminescent properties of Eu3+, Tb3+, Dy3+, Sm3+ and Tm3+ in the matrices of Ca4Y6(SiO4)6O were investigated. The bands at about 173 nm in the vacuum ultraviolet excited spectra were attributed to host lattice absorption of the matrix Ca4Y6(SiO4)6O. For Eu3+-doped samples, the O2− → Eu3+ CTB was identified at 258 nm. Typical 4f–5d absorption bands in the region of 195–300 nm were observed in Tb3+-doped samples. For Dy3+-doped and Sm3+-doped samples, the broad excitation bands consisted of host absorptions, CTB and f–d transition. For Tm3+-doped samples, the O2− → Tm3+ CTB was located at 191 nm. About the color purity and emission intensity, Ca4Y6(SiO4)6O:Tb3+ is an attractive candidate of green light PDP phosphor, and Ca4Y6(SiO4)6O:Dy3+ has potential application in the field of mercury-free lamps.Highlights► Luminescence properties of rare earths ions doped CYS are investigated. ► Rare earths ions doped CYS exhibit multicolor emissions under 172 nm excitation. ► HAB appears in the excitation spectra, revealing the host sensitized luminescence. ► CYS:RE3+ enriches the phosphors for PDPs and Hg-free lamps applications.
Co-reporter:Bitao Liu, Boyu Han, Feng Zhang, Yan Wen, Ge Zhu, Jia Zhang, Yuhua Wang
Materials Research Bulletin 2012 47(1) pp: 156-159
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.09.021
Co-reporter:Y. Li, Y. Wang, Y. Gong, X. Xu, F. Zhang
Acta Materialia 2011 Volume 59(Issue 8) pp:3174-3183
Publication Date(Web):May 2011
DOI:10.1016/j.actamat.2011.01.057
Abstract
The fluorescence, phosphorescence and thermoluminescence properties of Eu-doped BaMgSiO4 phosphors sintered in air and in a reducing atmosphere were investigated. Phosphorescence of phosphor sintered in a reducing atmosphere can last for 1.5 h at a recognizable intensity level, whereas phosphorescence of air-sintered phosphor can only persist for 6 min. In addition, a distinction between the shape of the fluorescence spectrum and its corresponding phosphorescence spectrum is observed in the former case. Ionization of Eu2+ to Eu3+ upon UV irradiation is observed in the phosphor prepared in a reducing atmosphere, but there is no indication that the photogenerated Eu3+ cannot change back to its divalent state at room temperature after the excitation source is switched off. In addition, phosphor sintered in a reducing atmosphere shows photochromism upon UV irradiation. No such photoionization and photochromism behavior is observed for the air-sintered phosphor. A possible Eu2+ photoionization mechanism is constructed on the basis of these experimental observations. The photoionization mechanism presented can also successfully explain the fluorescence and phosphorescence behavior of Eu in BaMgSiO4.
Co-reporter:Linshui Wang, Yuhua Wang
Journal of Luminescence 2011 Volume 131(Issue 7) pp:1479-1481
Publication Date(Web):July 2011
DOI:10.1016/j.jlumin.2011.03.028
Single-phased Sr3B2SiO8:Eu3+ phosphor was prepared by a solid-state method at 1020 °C. The luminescence spectra showed that Sr3B2SiO8:Eu3+ phosphor can be effectively excited by near ultraviolet light (393 nm) and blue light (464 nm). When excited at 393 or 464 nm Sr3B2SiO8:Eu3+ exhibited the main emission peaks at 611 and 620 nm, which resulted from the supersensitive 5D0→7F2 transition of Eu3+. The luminescence intensity of Sr3B2SiO8:Eu3+ at 611 and 620 nm reached the maximum when the doping content of Eu3+ was 4.5 mol%. Its chromaticity coordinates (0.646, 0.354) were very close to the NTSC standard values (0.67, 0.33). Thus, Sr3B2SiO8:Eu3+ is considered to be an efficient red-emitting phosphor for long-UV InGaN-based light-emitting diodes.Highlights► Sr3B2SiO8:Eu3+ was synthesized using solid-state reaction method for the first time. ► The phosphor can be efficiently excited by the near-UV chips and gives strong red emission. ► The phosphor is a potential candidate for white light-emitting diodes applications.
Co-reporter:Zhaofeng Wang, Yuhua Wang, Yezhou Li, Bitao Liu
Journal of Alloys and Compounds 2011 Volume 509(Issue 2) pp:343-346
Publication Date(Web):12 January 2011
DOI:10.1016/j.jallcom.2010.09.023
BaMgAl10O17:Eu2+ nanorods were synthesized by sol–gel technique, and their luminescent properties were investigated upon the irradiation of vacuum ultraviolet (VUV) light. By introducing surfactant cetyl-tri-methyl-ammonium bromide (CTAB) in sol–gel process and additional Mg2+ in the raw materials, the emission intensity and thermal stability of the nanophosphor were both enhanced. The above improvements made it possible that the nanosized BAM phosphor could be a good alternative for PDP application.Research highlights▶ BaMgAl10O17: Eu2+ nanorods were synthesized by sol-gel process. ▶ Luminescent intensity was enhanced by introducing CTAB. ▶ Thermal stability was improved by introducing Mg2+. ▶ The optimum nanorods could be applied in high resolution plasma display panels.
Co-reporter:Jia Zhang, Yuhua Wang, Yan Huang
Optical Materials 2011 Volume 33(Issue 8) pp:1325-1330
Publication Date(Web):June 2011
DOI:10.1016/j.optmat.2011.03.022
Novel Tb3+ and Mn2+ activated Ca8MgGd(PO4)7 phosphors were synthesized by solid-state reaction and their photoluminescence properties in vacuum ultraviolet region were investigated for the first time. It can be observed from the excitation spectra that the host-related absorption band is located around 170 nm, and it overlaps the O2− → Tb3+ charge transfer band of Ca8MgGd(PO4)7:Tb3+ around 161 nm and the 3d5 → 3d44s transition band of Ca8MgGd(PO4)7:Mn2+ near 200 nm. The 4f–4f 5d spin-allowed and spin-forbidden transitions of Tb3+ are verified to be located at 170–250 and 257–271 nm, respectively. Upon 147 nm excitation, the dominant emission peak intensity of the Ca8MgGd0.1(PO4)7:0.9Tb3+ phosphor is about 2.7 times stronger than that of the commercial Zn2SiO4:Mn2+ green phosphor, and the brightness of the former with a short decay time of 2.5 ms is about 98% of the latter’s. The Ca8MgGd(PO4):Mn2+ phosphor excited at 147 nm exhibits a deep red emission around 650 nm, which could be attributed to the 4T1 → 6A1 transition of Mn2+, with the CIE index (0.679, 0.321). In a word, the results above indicate that both Tb3+ and Mn2+ activated Ca8MgGd(PO4)7 phosphors could be promising for PDP or Hg-free lamp applications.Highlights► The Ca8MgGd(PO4)7:Tb3+ shows a comparable brightness with commercial Zn2SiO4:Mn2+. ► The Ca8MgGd(PO4)7:Tb3+ shows a shorter decay time than commercial Zn2SiO4:Mn2+. ► The Ca8MgGd(PO4)7:Tb3+, Mn2+ can be promising for PDP or Hg-free lamp application.
Co-reporter:Jun Zhou, Yuhua Wang, Bitao Liu, Jidi Liu
Journal of Physics and Chemistry of Solids 2011 Volume 72(Issue 9) pp:995-1001
Publication Date(Web):September 2011
DOI:10.1016/j.jpcs.2010.08.017
BaMgAl10O17:Eu2+ phosphors were synthesized by the flux method. When the appropriate amounts of fluxes are added, the synthesis temperature reduced by at least 200 °C compared with the conventional solid-state reaction method. SEM images demonstrated that addition of the flux in the process of phosphor synthesis benefitted the size and morphology of BaMgAl10O17:Eu2+ phosphor particles. Photoluminescence measurements under VUV excitation indicated that the luminescent intensity of the phosphor enhanced by adding the flux system (BaF2+Li2CO3). Addition of the flux system can not only enhance the luminescence efficiency and improve the stability, but also control the morphology and grain size of the phosphor. Replacement of Ba2+ by Li+ could generate traps, which result in slightly longer decay time.
Co-reporter:Jia Zhang, Yuhua Wang, Linna Guo, Feng Zhang, Yan Wen, Bitao Liu, Yan Huang
Journal of Solid State Chemistry 2011 Volume 184(Issue 8) pp:2178-2183
Publication Date(Web):August 2011
DOI:10.1016/j.jssc.2011.06.014
Tb3+, Yb3+, Tm3+, Er3+, and Ho3+ doped Ca3(PO4)2 were synthesized by solid-state reaction, and their luminescence properties were studied by spectra techniques. Tb3+-doped samples can exhibit intense green emission under VUV excitation, and the brightness for the optimal Tb3+ content is comparable with that of the commercial Zn2SiO4:Mn2+ green phosphor. Under near-infrared laser excitation, the upconversion luminescence spectra of Yb3+, Tm3+, Er3+, and Ho3+ doped samples demonstrate that the red, green, and blue tricolored fluorescence could be obtained by codoping Yb3+–Ho3+, Yb3+–Er3+, and Yb3+–Tm3+ in Ca3(PO4)2, respectively. Good white upconversion emission with CIE chromaticity coordinates (0.358, 0.362) is achieved by quadri-doping Yb3+–Tm3+–Er3+–Ho3+ in Ca3(PO4)2, in which the cross-relaxation process between Er3+ and Tm3+, producing the 1D2–3F4 transition of Tm3+, is found. The upconversion mechanisms are elucidated through the laser power dependence of the upconverted emissions and the energy level diagrams.Graphical abstractThe CPO:0.25Tb3+, 0.25Na+ exhibits a comparable brightness to the commercial Zn2SiO4:Mn2+ upon 147 nm excitation. Good white light color is achieved in CPO:Yb3+–Tm3+–Er3+–Ho3+ under 980 nm excitation.Highlights► Ca3(PO4)2:Tb3+,Na+ exhibits a comparable brightness with commercial Zn2SiO4:Mn2+. ► Red, green and blue colors are achieved in Yb3+, Ho3+, Er3+, Tm3+ doped Ca3(PO4)2. ► Good white emission is obtained in Yb3+–Ho3+–Er3+–Tm3+ quadri-doped Ca3(PO4)2. ► Ca3(PO4)2:Tb3+, Yb3+, Ho3+, Er3+, Tm3+ could be potential phosphors.
Co-reporter:Wei Liang, Yuhua Wang
Materials Chemistry and Physics 2011 Volume 127(1–2) pp:170-173
Publication Date(Web):16 May 2011
DOI:10.1016/j.matchemphys.2011.01.052
Pr3+, Mn2+ co-doped K2YZr(PO4)3 samples were prepared by solid-state reaction method and their photoluminescence (PL) properties were investigated in ultra-violet (UV) and vacuum ultra-violet (VUV) region. The results indicated that in Pr3+ singly doped K2YZr(PO4)3 sample, the first-step transition (1S0 → 1I6, 3PJ around 405 nm) of Pr3+ is near the ultraviolet (UV) range, not useful for practical application. When Mn2+ was doped as a co-activator ion, the energy of 1S0 → 1I6, 3PJ transition can be transferred synchronously from Pr3+ to Mn2+ and then emit a visible photon. The optimal quantum efficiency (QE) of this co-doped system K2YZr(PO4)3: Pr3+, Mn2+ reached to 126.3%, suggesting a novel type of practical visible quantum cutting phosphor in promising application.Research highlights► Pr3+, Mn2+ co-doped K2YZr(PO4)3 phosphor is a novel type of practical visible quantum cutting phosphor in promising application. ► The optimal quantum efficiency (QE) of this co-doped system K2YZr(PO4)3: Pr3+, Mn2+ reached to 126.3%. ► The Mn2+6A1g → 4Eg–4A1g transition was found to coincide well with the 1S0 → 1I6 transition of Pr3+. ► The energy transfer from Pr3+ to Mn2+ was also observed, converting the first photon from the PCE of Pr3+ into the red emission of Mn2+, and the QC process occurred in this Pr3+, Mn2+ co-doped K2YZr(PO4)3 phosphor.
Co-reporter:Yu Gong, Yuhua Wang, Xuhui Xu, Yanqin Li, Shuangyu Xin, Liurong Shi
Optical Materials 2011 Volume 33(Issue 11) pp:1781-1785
Publication Date(Web):September 2011
DOI:10.1016/j.optmat.2011.06.015
Eu2+, Mn2+ and Dy3+ co-doped long-lasting phosphors Sr3MgSi2O8 were prepared by a solid-state reaction under a reductive atmosphere. Fluorescence spectra demonstrated that the weak red emission resulting from the forbidden transition of Mn2+ could be enhanced by the energy transfer from Eu2+ to Mn2+. The energy transfer between Eu2+ and Mn2+ was systematically investigated. The phosphorescence spectra revealed that Eu2+ could persistently transfer its energy to Mn2+ after removing the excitation source. The duration of Mn2+ can prolong to more than 2 h. The thermoluminescence spectra were used to characterize the ability of the trap to trapping the carriers. By the analysis of the ionization potentials, the roles of Mn2+ and Dy3+ in the afterglow process were discussed. A possible afterglow mechanism was presented and discussed.Highlights► Through the energy transfer from Eu2+ to Mn2+, the duration of Mn2+ can prolong to more than 2 h. ► The electron trap plays a dominate role for the long-persistence phosphorescence. ► The Sr3MgSi2O8:Eu2+, Mn2+, Dy3+ can be a promising candidate for the red-light long-lasting phosphor.
Co-reporter:Yan Wen, Yuhua Wang, Feng Zhang, Bitao Liu
Materials Chemistry and Physics 2011 Volume 129(Issue 3) pp:1171-1175
Publication Date(Web):3 October 2011
DOI:10.1016/j.matchemphys.2011.05.078
The present investigation aims to demonstrate the potentiality of Tb3+ and Ce3+ co-doped Ca4Y6(SiO4)6O phosphors. By incorporation of Ce3+ into Ca4Y6(SiO4)6O: Tb3+, the excitation band was extended from short-ultraviolet to near-ultraviolet region. The energy transfer from Ce3+ to Tb3+ in Ca4Y6(SiO4)6O host was investigated and demonstrated to be a resonant type via a dipole–dipole mechanism with the critical distance of 10.2 Å. When excited by 352 nm, Ca4Y6(SiO4)6O: Ce3+, Tb3+ exhibited a brighter and broader violet-blue emission (421 nm) from the Ce3+ and an intense green emission (542 nm) from the Tb3+. Combining the two emissions whose intensities were adjusted by changing the doping levels of the co-activator, an optimized white light with chromaticity coordinates of (0.278, 0.353) is generated in Ca4Y6(SiO4)6O: 2% Ce3+, 8% Tb3+, and this phosphor could be potentially used in near-ultraviolet light-emitting diodes.Highlights► Ca4Y6(SiO4)6O: Ce3+, Tb3+ shows good luminescence properties under UV excitation. ► Efficient energy transfer from Ce3+ to Tb3+ in this phosphor is observed obviously. ► The mechanism of energy transfer is demonstrated to be a resonant dipole–dipole interaction. ► Ca4Y6(SiO4)6O: 2%Ce3+, 8%Tb3+ exhibits excellent white emission under 352 nm excitation. ► This kind of phosphor can be potentially used in near-UV pumped LEDs.
Co-reporter:Feng Zhang, Yuhua Wang, Yan Wen, Dan Wang, Ye Tao
Optical Materials 2011 Volume 33(Issue 3) pp:475-479
Publication Date(Web):January 2011
DOI:10.1016/j.optmat.2010.10.035
RE3+-activated monoclinic Na3GdP2O8 (RE3+ = Tb3+, Dy3+, Eu3+, Sm3+) phosphors have been synthesized by a solid-state reaction method. Their photoluminescence properties in the vacuum ultraviolet (VUV) region were investigated. By analyzing their excitation spectra, the host-related absorption band was determined to be around 166 nm. The f–d transition bands and the charge transfer bands for Na3GdP2O8:RE3+ (RE3+ = Tb3+, Dy3+, Eu3+, Sm3+) were assigned and corroborated. For the sample Na3GdP2O8:5%Tb3+, the strong bands at around 202 and 221 nm are assigned to the 4f–5d spin-allowed transitions and the weak band at 266 nm is related to the spin-forbidden transition of Tb3+. For Na3GdP2O8:5%Dy3+, the broad band at 176 nm could be related to the f–d transitions of Dy3+ and the O2− → Dy3+ charge transfer band (CTB) besides the host-related absorption. In the excitation spectrum of Eu3+ doped sample, the O2− → Eu3+ CTB is observed to be at 245 nm. For the Sm3+ doped sample, the O2− → Sm3+ CTB is not distinguished obviously and is overlapped with the host-related absorption band.
Co-reporter:Wenjie Wang, Bitao Liu, Yuhua Wang, Zhiya Zhang, Yousan Chen, Lan Wei
Materials Letters 2011 Volume 65(23–24) pp:3580-3582
Publication Date(Web):December 2011
DOI:10.1016/j.matlet.2011.07.080
The blue phosphor Ba0.9 Mg0.98Al10O17:0.1Eu2+, 0.02Mn2+ (BAM:Eu2+, Mn2+) was prepared by flux assisted solid-state reaction method. The effects of (NH4)2CO3 and LiF on the morphology and luminescent properties were studied. The usually obtained BAM:Eu2+, Mn2+ particles had hexagonal shape. We found that the thickness of the particle was affected by the amount of LiF and spherical-like particles can be obtained. The significant change on morphology from plate-like to spherical-like shape led to a highly enhanced luminescence of BAM:Eu2+, Mn2+. The maximum luminance intensity of prepared samples was 108% in comparison with the commercial BAM:Eu2+, Mn2+ under UV excitation.Highlights► The thickness of the plate-like BAM was affected by the amount of LiF flux. ► Spherical-like BAM particles with hexagonal surface could be obtained. ► The maximum luminance of the samples was 108% in comparison with commercial BAM.
Co-reporter:Jia Zhang, Yuhua Wang
Materials Chemistry and Physics 2011 130(3) pp: 1265-1269
Publication Date(Web):
DOI:10.1016/j.matchemphys.2011.09.009
Co-reporter:Jia Zhang, Yuhua Wang, Yan Wen, Feng Zhang, Bitao Liu
Materials Research Bulletin 2011 46(12) pp: 2554-2559
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.08.002
Co-reporter:Yurong Shi, Zhigang Yang, Wenjie Wang, Ge Zhu, Yuhua Wang
Materials Research Bulletin 2011 46(7) pp: 1148-1150
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.03.001
Co-reporter:Feng Zhang, Yuhua Wang, Bitao Liu, Yan Wen, Ye Tao
Materials Research Bulletin 2011 46(5) pp: 722-725
Publication Date(Web):
DOI:10.1016/j.materresbull.2011.01.020
Co-reporter:Jie Li, Yuhua Wang, Bitao Liu
Journal of Luminescence 2010 Volume 130(Issue 6) pp:981-985
Publication Date(Web):June 2010
DOI:10.1016/j.jlumin.2010.01.009
The red-emitting Y0.65−xGd0.25MxBO3:0.10Eu3+ (M=Li, Na, K 0.00≤x≤0.10) phosphors were synthesized by solid-state reaction and their photoluminescence characteristics were studied under vacuum ultraviolet (VUV) excitation. The emission intensity is significantly improved by adding alkali metal ions dopants because they introduce some bounded electron−hole pairs, which act as an intermediator for the excitation energy transfer from the host lattice to the activator Eu3+. The chromaticity was improved due to the distorted surrounding of Eu3+. The emission intensity of the Y0.65−xGd0.25 MxBO3:0.10Eu3+ increased up to maximum with alkali metal ions doped to a certain concentration and then decreased with the increase in of alkali metal dopants.
Co-reporter:Huijuan Zhang, Yuhua Wang, Lechun Xie
Journal of Luminescence 2010 Volume 130(Issue 11) pp:2089-2092
Publication Date(Web):November 2010
DOI:10.1016/j.jlumin.2010.05.032
The photoluminescence of Tb3+ doped M and M′ type gadolinium orthotantalate Gd1−xTbxTaO4 (0.01≤x≤0.20) was investigated under ultraviolet and vacuum ultraviolet excitation. For the samples of Gd1−xTbxTaO4 with different crystallographic structures, emission spectra were the same in addition to intensity; the optimal concentration for Tb3+ was about 10 mol % in M type Gd1−xTbxTaO4 but 5 mol % in M′ type Gd1−xTbxTaO4. These differences could be corresponding with the difference in structures. In addition, compared to commercial Zn2SiO4: Mn2+, the integrated intensity of M and M′ type GdTaO4: Tb3+ could reach 67% and 85%, respectively, of that at 147 nm excitation, which indicates that GdTaO4: Tb3+ would be a promising vacuum ultraviolet phosphor for application in PDP and Hg-free lamp.
Co-reporter:Jidi Liu, Yuhua Wang, Xue Yu, Jie Li
Journal of Luminescence 2010 Volume 130(Issue 11) pp:2171-2174
Publication Date(Web):November 2010
DOI:10.1016/j.jlumin.2010.06.014
A series of green phosphors Zn1.92−2xYxLixSiO4:0.08Mn2+ (0≤x≤0.03) were prepared by solid-state synthesis method. Phase and lattice parameters of the synthesized phosphors were characterized by powder X-ray diffractometer (XRD) and the co-doped effects of Y3+/Li+ upon emission intensity and decay time were investigated under 147 nm excitation. The results indicate that the co-doping of Y3+/Li+ has favorable influence on the photoluminescence properties of Zn2SiO4:Mn2+, and the optimal photoluminescence intensity of Zn1.90Y0.01Li0.01SiO4:0.08Mn2+ is 103% of that of commercial phosphor when the doping concentration of Y3+/Li+ is 0.01 mol. Additionally, the decay time of phosphor is much shortened and the decay time of Zn1.90Y0.01Li0.01SiO4:0.08Mn2+ is 3.39 ms, shorter by 1.83 ms than that of commercial product after Y3+/Li+ co-doping.
Co-reporter:Ye Zhou Li, Yu Hua Wang, Zhao Feng Wang, Zhi Ya Zhang
Journal of Luminescence 2010 Volume 130(Issue 7) pp:1225-1229
Publication Date(Web):July 2010
DOI:10.1016/j.jlumin.2010.02.029
Tm3+ doped β-rhenanite (β-NaCaPO4) series were synthesized by solid-state reaction. The crystalline structure of β-rhenanite was simulated and the photoluminescence properties of NaCa1-xPO4:xTm3+ (0
Co-reporter:Wei Liang, Yuhua Wang
Materials Chemistry and Physics 2010 Volume 119(1–2) pp:214-217
Publication Date(Web):15 January 2010
DOI:10.1016/j.matchemphys.2009.08.058
K2Gd1−xZr(PO4)3:Eux3+ (0.02 ≤ x ≤ 0.1, x is in mol.%) were prepared by solid-state reaction method and their photoluminescence properties were investigated in ultra-violet (UV) and vacuum ultra-violet (VUV) region. The phenomenon of visible quantum cutting through downconversion was observed for the Gd3+–Eu3+ couple in this Eu3+-doped K2GdZr(PO4)3 system. Visible quantum cutting, the emission of two visible light photons per absorbed VUV photon, occurred upon the 186 nm excitation of Gd3+ at the 6GJ level via two-step energy transfer from Gd3+ to Eu3+ by cross-relaxation and sequential transfer of the remaining excitation energy. The results revealed that the efficiency of the energy transfer process from Gd3+ to Eu3+ in the Eu3+-doped K2GdZr(PO4)3 system could reach to 155% and K2GdZr(PO4)3:Eu3+ was effective quantum cutting material.
Co-reporter:Lingling Peng;Qizheng Dong;Zhaofeng Wang
Nano-Micro Letters 2010 Volume 2( Issue 3) pp:190-196
Publication Date(Web):2010 September
DOI:10.1007/BF03353640
Homogeneous ZnSe nanocrystals were prepared via surfactant-assisted hydrothermal method. Surfactants agent CTAB was used to control the particle morphology and the growth rate. The structure, morphology and optical properties of ZnSe nanocrystals have been investigated by XRD, TEM and luminescence spectroscopy. The results indicated that the size of ZnSe nanocrystals ranged from 3.0 nm to 5.0 nm with cubic zinc blende structure. ZnSe nanocrystals coated by CTAB were revealed high dispersibility and distribution under TEM. Compared to the bulk ZnSe, the absorption edges and photoluminescence peaks of ZnSe nanocrystals were blue shifted to higher energies due to the quantum confinement effect. The emission intensity was strengthened after coated CTAB compared to bare sample. This was mainly due to the surface passivation. Meanwhile, we simply explored the formation mechanism of ZnSe nanocrystal in hydrothermal system.
Co-reporter:Huihui Li
Research on Chemical Intermediates 2010 Volume 36( Issue 1) pp:51-59
Publication Date(Web):2010 January
DOI:10.1007/s11164-010-0113-x
CaAl2O4:Eu2+, Nd3+@TiO2 composite powders were synthesized by a sol–gel method under mild conditions (i.e. low temperature and ambient pressure). The as-prepared powders were characterized by transmission electron microscopy (TEM) and analyzed by X-ray diffraction (XRD). The photocatalytic behavior of the TiO2-base surfaces was evaluated by the degradation of nitrogen monoxide gas. It suggested that CaAl2O4:Eu2+, Nd3+@TiO2 composite powders were composed of anatase titania and that CaAl2O4:Eu2+, Nd3+. TiO2 particles were deposited on the surface of CaAl2O4:Eu2+, Nd3+ to form uniform film. CaAl2O4:Eu2+, Nd3+@TiO2 composite powders exhibited higher photocatalytic activity compared with pure TiO2 under visible light. And the result also clearly indicated that the long afterglow phosphor absorbed and stored lights for the TiO2 to remain photocatalytic activity in the dark.
Co-reporter:Bin Liu;Shu Yin;Tsugio Sato
Research on Chemical Intermediates 2010 Volume 36( Issue 1) pp:39-49
Publication Date(Web):2010 January
DOI:10.1007/s11164-010-0112-y
Nitrogen-doped titania was coupled with the commercial titania nanoparticles by mechanical milling in liquid medium. The as-prepared nanocomposites (TiO2/TiO2−xNy) were characterized by X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET) specific surface area, UV–Vis spectroscopy, chemiluminescence, and acetaldehyde decomposition activity techniques. When a small amount of nitrogen-doped titania was added into the commercial titania, higher intensity and longer lifetime of 1O2 was observed, and the photocatalytic activity was efficiently improved. The TiO2−xNy acts as the acceptor of photoinduced holes. The recombination of the electron-hole was effectively depressed by the heterogeneous electron transfer. This could be an effective way to obtain highly active photocatalysts.
Co-reporter:Yuhua Wang, Yan Wen, Feng Zhang
Materials Research Bulletin 2010 45(11) pp: 1614-1617
Publication Date(Web):
DOI:10.1016/j.materresbull.2010.07.013
Co-reporter:Lingling Peng
Nanoscale Research Letters 2010 Volume 5( Issue 5) pp:
Publication Date(Web):2010 May
DOI:10.1007/s11671-010-9572-7
Mn-doped ZnS nanocrystals based on low dopant concentrations (0–2%) and coated with a shell of Zn(OH)2 have been prepared via soft template and precipitation reaction. The results indicate that the ZnS:Mn nanocrystal is cubic zinc blende structure and its diameter is 3.02 nm as demonstrated by XRD. Measured by TEM, the morphology of nanocrystals is a spherical shape, and their particle size (3–5 nm) is similar to that of XRD results. Photoluminescence spectra under ultraviolet region shows that the volume ratio of alcohol to water in the template has a great effect on the luminescence properties of ZnS:Mn particles. Compared with unpassivated ZnS:Mn nanocrystals, ZnS:Mn/Zn(OH)2 core/shell nanocrystal exhibits much improved luminescence and higher absolute quantum efficiency. Meanwhile, we simply explore the formation mechanism of ZnS:Mn nanocrystals in alcohol and water system and analyze the reason why alcohol and water cluster structures can affect the luminescent properties of nanoparticle.
Co-reporter:Qizheng Dong, Yuhua Wang, Zhaofeng Wang, Xue Yu and Bitao Liu
The Journal of Physical Chemistry C 2010 Volume 114(Issue 20) pp:9245-9250
Publication Date(Web):May 4, 2010
DOI:10.1021/jp1002287
A series of different concentrations of Eu3+ doping in YBO3 nanophosphors were successfully prepared by a surfactant-assisted solvothermal and heat-treatment process. Their photoluminescence (PL) properties were investigated under vacuum ultraviolet (VUV) and ultraviolet (UV) excitation. In comparison with the change trend of emission intensities in UV spectra, we found a unique phenomenon in the VUV spectra of YBO3:Eu3+ nanophosphors: the PL intensities are not sensitive to the activator doping concentrations. Although the doping concentrations were changed in a large range (2.5−25%), the PL intensities were maintained in a certain value. This phenomenon was also not observed in the bulk YBO3 phosphor. We gave a detailed explanation to this phenomenon by using the “self-purification” effect in nanosystems. It indicated that the activator in the nanophosphor is not a homogeneous distribution but tends to gather on the surface, which will also cause effective activator amounts for VUV luminescence to be very low.
Co-reporter:Yanqin Li, Yuhua Wang, Xuhui Xu, Yu Gong
Journal of Luminescence 2009 Volume 129(Issue 10) pp:1230-1234
Publication Date(Web):October 2009
DOI:10.1016/j.jlumin.2009.06.014
Eu2+, Dy3+ co-doped Sr2MgSi2O7 phosphors with deficient, stoichiometric or excess amounts of silicon are prepared by solid-state reaction. XRD and SEM results indicate that all the samples studied are found to be free from impurities and samples with SiO2 excess possess better crystallinity and larger grain size. Photoluminescence reveals that the position of Eu2+ emission is not changed with various compositions. However, both photoluminescence intensity and afterglow properties are increased by an incorporation of excess SiO2 and are decreased by SiO2 deficiency. The thermoluminescence results show that the corresponding increase or decrease in afterglow is associated with trap density, but no change in trap depth. The underlying reason of photoluminescence and afterglow enhancement is discussed.
Co-reporter:Xiaolan Gao, Yuhua Wang, Dan Wang, Bitao Liu
Journal of Luminescence 2009 Volume 129(Issue 8) pp:840-843
Publication Date(Web):August 2009
DOI:10.1016/j.jlumin.2009.03.007
KGd1−x(WO4)2−y(MoO4)y:Eu3+x(0.1⩽x⩽0.75, y=0 and 0.2) phosphors are synthesized through traditional solid-state reaction and their luminescent properties in ultraviolet (UV) and vacuum ultraviolet (VUV) regions are investigated. Under 147 nm excitation, these phosphors show characteristic red emission with good color purity. In order to improve their emission intensity, the MoO42− (20 wt%) is introduced into the anion of KGd1−x(WO4):Eu3+x. The Mo6+ and Eu3+ co-doped KGd(WO4)2 phosphors show higher emission intensity in comparison with the singly Eu3+-doped KGd(WO4)2 in VUV region. The chromaticity coordination of KGd0.45(WO4):Eu3+0.55 is (x=0.669, y=0.331), while that of KGd0.45(WO4)1.8(MoO4)0.2:Eu3+0.55 is (x=0.666, y=0.334) in VUV region.
Co-reporter:Jun Zhou, Yuhua Wang, Bitao Liu, Yanghua Lu
Journal of Alloys and Compounds 2009 Volume 484(1–2) pp:439-443
Publication Date(Web):18 September 2009
DOI:10.1016/j.jallcom.2009.04.118
The green phosphor BaAl11.9O19:0.1Mn2+ (BHA) was prepared by flux assisted solid-state reaction method. The effect of H3BO3 and the fire conditions on the crystal structure and luminescent properties under vacuum ultraviolet region (VUV) excitation of the phosphor were studied. Results of XRD patterns indicated that a pure phase BaAl12O19 could be achieved at the firing temperature above 1300 °C doping H3BO3 of 7.0 wt% as flux. The additions of flux H3BO3 promoted the solid reaction and reduced the temperature forming BaAl12O19:Mn2+ phosphor. Photoluminescent measurements under VUV excitation indicated that the luminescent intensity of the BaAl11.9O19:0.1Mn2+ enhanced by solid-state reaction adding appropriate amounts of H3BO3 as a flux.
Co-reporter:Xue Yu, Yuhua Wang
Journal of Physics and Chemistry of Solids 2009 Volume 70(Issue 8) pp:1146-1149
Publication Date(Web):August 2009
DOI:10.1016/j.jpcs.2009.06.015
Nanoscaled Zn2SiO4:Mn2+ green phosphor with regular and uniform morphology was synthesized by hydrothermal method at a low temperature of 140 °C. The structure and morphology of the phosphor was characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The effects of the hydrothermal temperature and the time on the crystallite structure and the vacuum ultraviolet (VUV) photoluminescence (PL) properties were evaluated. The as-synthesized nanoscaled Zn2SiO4:Mn2+ phosphor exhibited intensive broad emission around 523 nm, which was attributed to the 4T1→6A1 transition of Mn2+. The PL intensity increased along with the increasing hydrothermal temperature and time. The heat-treated phosphors exhibited higher PL intensity than the corresponding samples prepared using the conventional solid-state reaction.
Co-reporter:Dan Wang, Yuhua Wang
Materials Chemistry and Physics 2009 Volume 115(2–3) pp:699-702
Publication Date(Web):15 June 2009
DOI:10.1016/j.matchemphys.2009.02.009
(Y,Tb)PO4 were prepared by solid state reaction and their photoluminescence (PL) spectra were investigated under vacuum ultraviolet (VUV) excitation. The obtained results indicate that (Y,Tb)PO4 can efficiently absorb the energy in the region of 112–243 nm and transfer it to the 5D4 energy level of Tb3+. After that, green light is emitted by Tb3+ due to the transitions from 5D4 energy level to the ground state. Under 147 nm excitation, the optimal emissive intensity is obtained when Tb3+ concentration is about 20%, which is about 110% of commercial phosphor Zn1.96SiO4:0.04Mn2+ with chromaticity coordinates of (0.354, 0.553) and the decay time of about 2.527 ms. According to the obtained experimental data, we tentatively explain the energy absorption, transfer and luminescent quenching for YPO4:Tb3+ under 147 nm excitation.
Co-reporter:Yuhua Wang, Zhiya Zhang, Jiachi Zhang, Yanghua Lu
Journal of Solid State Chemistry 2009 Volume 182(Issue 4) pp:813-820
Publication Date(Web):April 2009
DOI:10.1016/j.jssc.2009.01.006
Undoped and RE ions doped SrB2Si2O8 were successfully synthesized. After the application of UV and VUV spectroscopy measurements, we made a novel discovery that the emission of SrB2Si2O8:Eu prepared in air can be switched between red and blue by the different excitations. The information is that quite a part of Eu3+ was spontaneously reduced to Eu2+ in air. The PL properties of Eu2+ in VUV and Eu3+, Ce3+ and Tb3+ in UV–VUV region in SrB2Si2O8 were evaluated for the first time. The excitation mechanisms of the O2−–Eu3+ CT, Ce3+f–d and Tb3+f–d transitions in UV region as well as the Eu3+f–d, O2−–Ce3+ CT, O2−–Tb3+ CT transitions and the host lattice absorption in VUV region were established. In addition, first principles calculation within the LDA of the DFT was applied to calculate the electronic structure and linear optical properties of SrB2Si2O8 and the results were compared with the experimental data.The emissions of SrB2Si2O8:Eu prepared in air can be switched between the red (611 nm) and the blue (440 nm) by different excitations: under 254 nm excitation the Eu3+ red emission is dominant while under 365 nm excitation the Eu2+ blue emission presides at the emission spectra; when excited by 340 nm it emits almost the pure blue; and when excited by 395 nm the two emissions present nearly equivalent intensity.
Co-reporter:Guocai Han, Yuhua Wang, Chunfang Wu, Jiachi Zhang
Materials Research Bulletin 2009 44(12) pp: 2255-2257
Publication Date(Web):
DOI:10.1016/j.materresbull.2009.07.021
Co-reporter:Yu Gong, Yuhua Wang, Ziqiang Jiang, Xuhui Xu, Yanqin Li
Materials Research Bulletin 2009 44(9) pp: 1916-1919
Publication Date(Web):
DOI:10.1016/j.materresbull.2009.05.003
Co-reporter:Jiachi Zhang, Yuhua Wang, Zhiya Zhang, Xie Peng, Yanping Jiang, Huihui Li
Materials Research Bulletin 2009 44(4) pp: 953-955
Publication Date(Web):
DOI:10.1016/j.materresbull.2008.08.005
Co-reporter:Zhiya Zhang, Yuhua Wang
Journal of Luminescence 2008 Volume 128(Issue 3) pp:383-386
Publication Date(Web):March 2008
DOI:10.1016/j.jlumin.2007.09.006
Alkaline-earth silicate phosphors CaMgSi2xO6+2x:Eu2+ (1.00⩽x⩽1.20) were prepared by traditional solid-state reaction. The phosphors showed an intense blue emission centered around 453 nm, with both 254 and 147 nm excitations. The host absorption below 200 nm in the excitation spectra consisted of two bands around 160 and 190 nm. The band around 160 nm was ascertained to be associated with the SiO4-tetrahedra and MgO6-polyhedra, and that around 190 nm was due to the CaO8-polyhedra or some impurities. The incorporation of excess Si of less than 15% would not lead to formation of impurities and the results indicated that an appropriate Si excess could improve the Photoluminescence (PL) intensity in both ultraviolet (UV) and vacuum ultraviolet (VUV) regions
Co-reporter:Jing Gou, Yuhua Wang, Feng Li
Journal of Luminescence 2008 Volume 128(5–6) pp:728-731
Publication Date(Web):May–June 2008
DOI:10.1016/j.jlumin.2007.10.015
Dy3+-doped SrB4O7 phosphors were synthesized by solid-state reaction. The luminescence properties of white-light SrB4O7:Dy3+ under vacuum ultraviolet (VUV) excitation were firstly investigated. According to strong absorption around 147 nm in excitation spectra, energy can easily be transferred to the energy levels of Dy3+ from host absorption, and hence luminescence of SrB4O7:Dy3+ under VUV excitation was effective, and it has the potential of being applied to a white lamp-house for mercury-free lamp.
Co-reporter:Zhiya Zhang, Yuhua Wang, Jiachi Zhang
Materials Letters 2008 Volume 62(6–7) pp:846-848
Publication Date(Web):15 March 2008
DOI:10.1016/j.matlet.2007.06.075
The new green-emitting phosphors Na3Y1 − xSi3O9:xTb3+ (0.05 ≦ × ≦ 0.50) were developed by a solid-state reaction in this study. The excitation in VUV region showed a broad band in 150–180 nm with the strong absorption at around 149 and 178 nm, which are adjacent to the VUV excitation light sources of 147 and 172 nm. The composition of Na3Y0.6Si3O9:0.4Tb3+ was observed to have the strongest emission around 541 nm. It showed the higher emission intensity, comparable brightness and a much shorter decay time under 147 nm excitation when compared with the commercial Zn2SiO4:Mn2+ green phosphor. The results indicated that Na3YSi3O9:Tb3+ could be potential candidate as a green-emitting VUV phosphor.
Co-reporter:Jiachi Zhang, Yuhua Wang, Zhiya Zhang, Zhilong Wang, Bin Liu
Materials Letters 2008 Volume 62(Issue 2) pp:202-205
Publication Date(Web):31 January 2008
DOI:10.1016/j.matlet.2007.04.101
The quenching concentrations of 5D4–7F6 emission of Tb3+ in (Gd,Y)BO3:Tb under 130–290 nm excitation were systematically investigated. The results revealed that its quenching concentrations of luminescence excited at particular wavelengths are dependent on corresponding excitation bands. Resulting in a calculation of coupling interaction, it was found that the quenching concentrations at excitation regions due to electrostatic interaction are often small while those corresponding to exchange interaction are usually larger (> 10%). Moreover, the quenching concentrations are also influenced significantly by luminescence sensitization of Gd3+ and Y3+ ions. Based on these results, a possible photoluminescence quenching mechanism was proposed.
Co-reporter:Lingli Wang, Yuhua Wang, Dan Wang, Jiachi Zhang
Solid State Communications 2008 Volume 148(7–8) pp:331-335
Publication Date(Web):November 2008
DOI:10.1016/j.ssc.2008.08.032
The electronic structures of SrB4O7 and SrB4O7:Eu have been calculated by density functional method with the local density approximation. The respective contributions of cations and anionic groups to the band structures are evaluated. An indirect band gap of 9.71 eV and a direct gap of 11.18 eV at U are obtained for SrB4O7. The calculated total and partial densities of states indicate that the top valence band of SrB4O7 is mainly constructed from the O-2p state, and the low conduction band mostly originates from B-2p and Sr-4d states. From the calculation, we find that the host absorption of SrB4O7 in VUV region is from both the BO4 group and Sr–O charge transfer transition. With the doping of Eu3+, the energy band of SrB4O7 moves downwards and new energy levels appear in the band gap, which is consistent with the experimental band models.
Co-reporter:Lingli Wang, Yuhua Wang
Journal of Luminescence 2007 Volume 126(Issue 1) pp:160-164
Publication Date(Web):September 2007
DOI:10.1016/j.jlumin.2006.06.007
The luminescent properties of CaYBO4:Ln(Ln=Eu3+, Tb3+) were investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) region. The CT band of Eu3+ at about 245 nm blue-shifted to 230 nm in VUV excitation spectrum; the band with the maximum at 183 nm was considered as the host lattice absorption. For the sample of CaYBO4:0.08Tb3+, the bands at about 235 and 263 nm were assigned to the f–d transitions of Tb3+ and the CT band of Tb3+ was calculated according to Jφrgensen's theory. Under UV and VUV excitation, the main emission of Eu3+ corresponding to the 5D0–7F2 transition located at about 610 nm and two intense emission of Tb3+ from the 5D4–7F5 transition had been observed at about 542 and 552 nm, respectively. With the incorporation of Gd3+ into the host lattice of CaYBO4, the luminescence of Tb3+ was enhanced while that of Eu3+ was decreased because of their different excitation mechanism.
Co-reporter:Deyin Wang, Yuhua Wang, Lingli Wang
Journal of Luminescence 2007 Volume 126(Issue 1) pp:135-138
Publication Date(Web):September 2007
DOI:10.1016/j.jlumin.2006.06.001
Vacuum ultraviolet (VUV) excitation and photoluminescence (PL) properties of Sr(Y, Gd)2O4 doped with Eu3+ were studied. The excitation spectra of SrY1.9Eu0.1O4 and SrY1.0Gd0.9Eu0.1O4 had absorption in the VUV region with the absorption band edge at 149 nm, while the absorption of SrGd1.9Eu0.1O4 in the VUV region was weak, which could be due to the narrow host band gap and no efficient energy transfer occurred in the VUV region. The PL spectra of all samples exhibited the characteristic emission of Eu3+ with the red 5D0–7F2 transition (611 nm) being the most prominent group.
Co-reporter:Ling He, Yuhua Wang, Hui Gao
Journal of Luminescence 2007 Volume 126(Issue 1) pp:182-186
Publication Date(Web):September 2007
DOI:10.1016/j.jlumin.2006.06.004
The excitation spectra of M (M=Si4+, Ti4+) and Eu3+ co-doped BaZr(BO3)2, BaZrO3:Eu and La2Zr2O7:Eu in the vacuum ultraviolet (VUV) regions of 110–300 nm are investigated and the host-lattice absorption are characterized. The result indicated that BaZr(BO3)2:Eu3+ phosphor has a strong absorption under the VUV excitation, and in the host-lattice excitation, the strong band at 130–160 nm could be due to the BO3 atomic groups; the band at 160–180 nm is related to the excitation of Ba–O; 180–200 nm corresponds to the charge transfer (CT) transition of Zr–O. The band at 200–235 nm due to the CT band of Eu3+–O2− and a bond valence study explained the observed weak CT band of Eu3+–O2− in the excitation spectra of BaZr(BO3)2:Eu3+. The emission results show that Si4+ can sensitize luminescence in the host of BaZr(BO3)2:Eu but Ti4+ has no improvement effect on luminescence.
Co-reporter:Yuhua Wang, Chunfang Wu, Jie Wei
Journal of Luminescence 2007 Volume 126(Issue 2) pp:503-507
Publication Date(Web):October 2007
DOI:10.1016/j.jlumin.2006.09.006
Monoclinic LnPO4:Tb,Bi (Ln=La,Gd) phosphors were prepared by hydrothermal reaction and their luminescent properties under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation were investigated. LaPO4:Tb,Bi phosphor and GdPO4:Tb phosphor showed the strongest emission intensity under 254 and 147 nm excitation, respectively, because of the different energy transfer models. In UV region, Bi3+ absorbed most energy then transferred to Tb3+, but in VUV region it was the host which absorbed most energy and transferred to Tb3+.
Co-reporter:Jing Gou, Yuhua Wang, Feng Li
Journal of Luminescence 2007 Volume 127(Issue 2) pp:327-331
Publication Date(Web):December 2007
DOI:10.1016/j.jlumin.2007.01.016
The luminescence properties of BaZr(BO3)2:5% Eu were investigated under ultraviolet (UV) and vacuum ultraviolet (VUV) excitation and different luminescence behaviors were observed by different excitation energies. After the analyses of the luminescence spectra, the result indicates that Eu3+ occupying non-centrosymmetric sites Ba2+ can be excited preferentially under 254 nm excitation, while Eu3+ occupying centrosymmetric sites Zr4+ can be excited preferentially under 147 nm excitation.
Co-reporter:Chunfang Wu, Yuhua Wang, Wei Jie
Journal of Alloys and Compounds 2007 Volume 436(1–2) pp:383-386
Publication Date(Web):14 June 2007
DOI:10.1016/j.jallcom.2006.07.056
Tb doped LnPO4 (Ln = La, Gd) phosphors with monoclinic system were successfully prepared by mild hydrothermal reaction at 240 °C. The 543 nm emission of Tb3+ in GdPO4 is higher than in LaPO4. By comparison, it is found that the intensity of host absorption band of GdPO4:Tb is higher than that of LaPO4:Tb which is ascribed to the energy transfer efficiency between the PO43− molecule and Tb3+ is higher. The emission intensity of optimal composition of GdPO4:0.3Tb is comparable with that of commercial Zn2SiO4:0.04Mn phosphor. These results suggest that GdPO4:0.3Tb is a potential candidate for plasma display panels (PDPs) application.
Co-reporter:Chunfang Wu, Yuhua Wang
Materials Letters 2007 Volume 61(Issue 28) pp:5037-5039
Publication Date(Web):November 2007
DOI:10.1016/j.matlet.2007.03.099
Samples of ZrP2O7 doped with and without Tb in the form of cubic symmetry were prepared and their 147 nm excited emission spectra and excitation spectra for Zr and Tb emission were investigated. The O–Zr excitation band located at 175 nm recorded for Zr–O emission at about 280 nm was observed, but it was not observed when monitored at 543 nm emission of Tb. It indicated that the energy transfer from Zr–Tb did not occur. In addition there are two f–d transition bands of Tb located at 197 and 217 nm respectively in the excitation spectra.
Co-reporter:Zhan Hui Zhang, Yu Hua Wang
Materials Letters 2007 Volume 61(19–20) pp:4128-4130
Publication Date(Web):August 2007
DOI:10.1016/j.matlet.2007.01.035
Co-reporter:JiaChi Zhang;ZhiYa Zhang;DeYin Wang;ZhiPeng Cl
Science Bulletin 2007 Volume 52( Issue 16) pp:2297-2300
Publication Date(Web):2007 August
DOI:10.1007/s11434-007-0329-3
The photoluminescence quenching behaviors of 5D3-7FJ and 5D4-7FJ (J = 0–6) transitions of Tb3+ in YBO3:Tb under 130–290 nm excitation were systematically investigated. The results revealed that the quenching concentrations of both 5D3-7FJ and 5D4-7FJ transitions of Tb3+ in YBO3:Tb were mainly dependent on excitation wavelength. Particularly, the quenching concentrations of 5D4-7FJ transitions of Tb3+ under 130–290 nm excitation were correlated with excitation bands of YBO3:Tb. The quenching concentrations of 5D3-7FJ transitions remained at low concentration (2%) under 186–290 nm excitation and then increased gradually with energy of incoming excitation photon when excited at 130–186 nm. This dependence should be involved in their excitation mechanisms and quenching pathway in particular excitation region.
Co-reporter:Lingli wang, Yuhua Wang
Materials Science and Engineering: B 2007 Volume 139(2–3) pp:232-234
Publication Date(Web):15 May 2007
DOI:10.1016/j.mseb.2007.03.001
The new borate phosphors Na2Y2B2O7:Eu3+ and YCa3(AlO)3(BO3)4:Eu3+ were synthesized and their luminescence properties were investigated under vacuum ultraviolet (VUV) excitation. Under VUV excitation, strong orange emission of 5D0 → 7F1 at 592 nm was observed in the emission spectrum of Na2Y2B2O7:Eu3+ and the best concentration for Eu3+ was 10%. While strong red emission of 5D0 → 7F2 transitions at 621 nm was observed for YCa3(AlO)3(BO3)4:Eu3+ and the most intense emission obtained at the concentration of 8%. The broad bands at 210–230 nm in their excitation spectra were attributed to the charge transfer band of Eu3+, and the two bands at 150–170 nm were assigned to the absorption of the host lattice. With the incorporation of Gd3+, the luminescence intensity of Eu3+ was improved greatly in both of the two host materials.
Co-reporter:Yuhua Wang, Lingli Wang
Materials Letters 2006 Volume 60(21–22) pp:2645-2649
Publication Date(Web):September 2006
DOI:10.1016/j.matlet.2006.01.056
The single phases of Y0.95 − xMxBO3:5%Eu3+ (M = Ca, Sr, Ba, Zn, Al, 0 ≤ x ≤ 0.1) were synthesized successfully by solid-state reaction. Their luminescent properties were studied under UV and VUV excitation. The results indicated that with the incorporation of Ca2+, Sr2+, Ba2+, Zn2+ or Al3+ into the host lattice of YBO3:Eu3+, the high symmetry around Eu3+ was destroyed and the ratio of red emission(5D0–7F2) to orange one (5D0–7F1) increased, leading to a better chromaticity. Furthermore, the co-doping ions such as Ca2+, Zn2+ and Al3+ were beneficial to enhance the luminescent intensity of Eu3+. These phenomena were evaluated, and possible explanations were proposed.
Co-reporter:Yuhua Wang, Hui Gao
Journal of Solid State Chemistry 2006 Volume 179(Issue 6) pp:1870-1873
Publication Date(Web):June 2006
DOI:10.1016/j.jssc.2006.02.025
SrZnO2:Eu3+ has been synthesized by solid-state reaction and its photoluminescence in ultraviolet (UV)–vacuum ultraviolet (VUV) range was investigated. The broad bands around 254 nm are assigned to CT band of Eu3+–O2−. With the increasing of Eu3+ concentration, Eu3+ could occupy different sites, which leads to the broadening of CT band. A sharp band is observed in the region of 110–130 nm, which is related to the host absorption. The phosphors emit red luminescence centered at about 616 nm due to Eu3+5D0→7F2 both under 254 and 147 nm, but none of Eu2+ blue emission can be observed.XRD pattern of SrZnO2 sintered at 1000 °C for 2 h.
Co-reporter:Dan Wang, Yuhua Wang
Materials Science and Engineering: B 2006 Volume 133(1–3) pp:218-221
Publication Date(Web):25 August 2006
DOI:10.1016/j.mseb.2006.05.008
In order to investigate the energy migration mechanisms of Eu3+ doped hexagonal KCaY(PO4)2 in vacuum ultraviolet (VUV) region, KCaY1−x(PO4)2:Eux3+ (0 ≪ x < 0.1) are prepared and their photoluminescence (PL) properties are evaluated under 147 nm excitation. Monitored by 616 nm emission, the weak band around 136–162 nm in the excitation spectra of KCaY0.95(PO4)20.05:Eu3+ could be assigned to the absorption of PO43−. The sharp peak at 213 nm which overlaps with the charge transition band (CTB) of Eu3+–O2− at about 177–280 nm should be assigned to the transition to 3H4 levels of Eu3+. Under 147 nm excitation the strongest emission peak is located at about 616 nm. When x reaches 0.05 in KCaY1−x(PO4)2:Eux3+(0 < x < 0.1), the optimum emission intensity is obtained. A main reason for the low quenching concentration of Eu3+ is that Eu3+ occupies not only the Y3+ position but also the K+ and Ca2+ sites, so the energy migration among Eu3+ ions could be in three-dimensional.
Co-reporter:Yuhua Wang, Xuan Guo, Tadashi Endo, Yukio Murakami, Mizumoto Ushirozawa
Journal of Solid State Chemistry 2004 Volume 177(Issue 7) pp:2242-2248
Publication Date(Web):July 2004
DOI:10.1016/j.jssc.2004.03.003
A broad excitation band in an excitation spectrum of (Gd,Y)BO3:Eu was observed in the VUV region. It could be considered that this band was composed of two bands at about 160 and 166 nm. The preceding band was assigned to the BO3 group absorption. The later one at about 166 nm could be assigned to the charge transfer (CT) transition of Gd3+–O2−. Such an assignment was deduced from the result that broadbands at around 170 nm for GdAlO3:Eu, and at 183 nm for Gd2SiO5:Eu are due to the CT transition of Gd3+–O2−; this was also identified by CaZr (BO3)2:Eu. Since there are no Gd3+ ions in it; a weak band in the VUV region in the excitation spectrum of Ca0.95ZrEu0.05(BO3)2 was observed. The excitation spectra were overlapped between the CT transition of Gd3+–O2− and BO3 group absorption, and it caused the emission of Eu3+ effectively in the trivalent europium-doped (Gd,Y)BO3 host lattice under 147 nm excitation. Intense broad excitation bands were observed at about 155 nm for YBO3:Eu and at about 153 nm for YAlO3:Eu; it could be attributed to the CT transition between Y3+ and O2−. As a result, under the xenon discharge (147 nm) excitation, the intense emission of Eu3+ in GdBO3 was found to be more convenient just because of the partial substitution of Y3+ for Gd3+.
Co-reporter:Yuhua Wang, Tadshi Endo, Erqing Xie, Deyan He, Bin Liu
Microelectronics Journal 2004 Volume 35(Issue 4) pp:357-361
Publication Date(Web):April 2004
DOI:10.1016/S0026-2692(03)00245-3
The luminescent properties of Ca4GdO(BO3)3:Eu3+ were investigated under excitation of UV and VUV light. Separate two broad bands at around 259 and 184 nm were observed in the excitation spectrum of Ca4GdO(BO3)3:Eu3+. These peaks were assigned to the charge transfer transition of Eu3+–O2− and Gd3+–O2−, respectively. Owing to the favorable spectral position in their broad intense excitation band, Eu3+ ions show a intense emission under 258 nm excitation in Ca4GdO(BO3)3:Eu3+. This spectral position was determined by the free oxygen ions O (1). Ca4GdO(BO3)3 doped with Eu3+ ion seems to be a preferable candidate as red lamp phosphor. On the other hand, a weak band with a maximum at about 184 nm was observed below 200 nm in the excitation spectrum of Ca4GdO(BO3)3:Eu3+. This phosphor do not emit effectively under the 147 nm excitation. This unfavorable profile was also due to the O (1) ions, which played a role to the shifting towards the lower energy sides. The luminescence of Eu3+ ions in Ca4GdO(BO3)3 was somewhat different from that observed in the other borates phosphors, but resembled to those observed in the oxide phosphors (e.g. Gd2O3, Y2O3 and Gd2SiO5). Such behavior was recognized by the detailed analysis of crystallographical surroundings around activator.
Co-reporter:Quansheng Wu, Jianyan Ding, Yanyan Li, Xicheng Wang, Yuhua Wang
Journal of Luminescence (June 2017) Volume 186() pp:
Publication Date(Web):June 2017
DOI:10.1016/j.jlumin.2017.02.016
The undoped and Eu2+/Ce3+ doped Ca3Li4-ySi2N6-yOy (0≤y≤1.5) (CLSN) were successfully prepared by solid-state reaction and their luminescence properties were studied. The undoped CLSN shows red defect-related luminescence with maximum emission intensity at 710 nm, Eu2+ and Ce3+ doped CLSN also show red emission centered at 702 nm and 673 nm, respectively. The electronic structure and the thermal stability of CLSN were investigated in this work. The results indicate that CLSN:Eu2+/Ce3+ could be conducive to the development of phosphor-converted light-emitting diodes.
Co-reporter:Linshui Wang, Yuhua Wang
Journal of Luminescence (July 2011) Volume 131(Issue 7) pp:1479-1481
Publication Date(Web):1 July 2011
DOI:10.1016/j.jlumin.2011.03.028
Single-phased Sr3B2SiO8:Eu3+ phosphor was prepared by a solid-state method at 1020 °C. The luminescence spectra showed that Sr3B2SiO8:Eu3+ phosphor can be effectively excited by near ultraviolet light (393 nm) and blue light (464 nm). When excited at 393 or 464 nm Sr3B2SiO8:Eu3+ exhibited the main emission peaks at 611 and 620 nm, which resulted from the supersensitive 5D0→7F2 transition of Eu3+. The luminescence intensity of Sr3B2SiO8:Eu3+ at 611 and 620 nm reached the maximum when the doping content of Eu3+ was 4.5 mol%. Its chromaticity coordinates (0.646, 0.354) were very close to the NTSC standard values (0.67, 0.33). Thus, Sr3B2SiO8:Eu3+ is considered to be an efficient red-emitting phosphor for long-UV InGaN-based light-emitting diodes.Highlights► Sr3B2SiO8:Eu3+ was synthesized using solid-state reaction method for the first time. ► The phosphor can be efficiently excited by the near-UV chips and gives strong red emission. ► The phosphor is a potential candidate for white light-emitting diodes applications.
Co-reporter:Xin Ding, Yuhua Wang
Optical Materials (February 2017) Volume 64() pp:
Publication Date(Web):February 2017
DOI:10.1016/j.optmat.2017.01.003
•Red emission Mg6ZnGeGa2O12: Mn4+ phosphors under NUV light are synthesized by high temperature solid-state reaction.•The structure and photoluminescence properties of them are investigated detailed.•Mg6ZnGeGa2O12: Mn4+ phosphors take on broad excitation and narrow emission.•It can emit red light peaking at 660 nm under NUV light with FWHM of 25 nm.A kind novel red emission Mg6ZnGeGa2O12: Mn4+ phosphor under NUV excitation is synthesized successfully by high temperature solid-state reaction. The structure of Mg6ZnGeGa2O12 is investigated by TEM and X-ray powder diffraction (XRD) Rietveld Refinement; the luminescence properties are measured by diffuse reflection spectra, emission spectra, excitation spectra, decay curves and temperature dependence spectra. The result indicated that it has one octahedral site and tetrahedral site in crystal structure. Mn4+ can occupy octahedral (Mg2+(Zn2+)/Ga3+) site. It can emit red light peaking at 660 nm under NUV (420 nm) excitation. The critical quenching concentration of Mn4+ was about 1.0 mol%. The concentration quenching mechanism investigates to be a d-d interaction for the Mn4+ center. The CIE chromaticity coordinates and FWHM are (0.717, 0.283) and 25 nm. The PL intensity of Mg6ZnGeGa2O12: 1.0%Mn4+ drops to 75% when the temperature is raised up to 150 °C. It implies that Mg6ZnGeGa2O12: Mn4+ is a potential red phosphor matching NUV LED chips.
Co-reporter:Yu Gong, Xuhui Xu, Wei Zeng, Cangji Wu, Yuhua Wang
Physics Procedia (2012) Volume 29() pp:86-90
Publication Date(Web):1 January 2012
DOI:10.1016/j.phpro.2012.03.696
The red light long-lasting phosphors BaMg2Si2O7: Ce3+, Mn2+, Dy3+ were synthesized by solid-state reactions under a weak reductive atmosphere. The energy transfer between Ce3+ and Mn2+ in BaMg2Si2O7 was systematically investigated. Through co-dope with Ce3+ in BaMg2Si2O7:Mn2+, Dy3+, the red phosphorescence of Mn2+ can prolong to more than 2 h. Two types of traps were existed in BaMg2Si2O7.
Co-reporter:Xuhui Xu, Yu Gong, Wei Zeng, Yuhua Wang
Physics Procedia (2012) Volume 29() pp:62-64
Publication Date(Web):1 January 2012
DOI:10.1016/j.phpro.2012.03.693
Long-lasting red phosphorescence and photostimulated luminescence in Ca2SnO4:Sm3+ were observed. The decay patterns of afterglow and thermoluminescence curves demonstrate that introduction of Gd3+ can increase the number of shallow traps and deep traps.
Co-reporter:Feng Zhang, Yuhua Wang, Ye Tao
Physics Procedia (2012) Volume 29() pp:55-61
Publication Date(Web):1 January 2012
DOI:10.1016/j.phpro.2012.03.692
A series of phosphors Li6Gd1-x(BO3)3:xTb3+ (0:x:1) was prepared by a conventional solid-state reaction method and their photoluminescence properties under VUV/UV excitation were demonstrated. For the excitation spectrum, the host-related absorption band, f-f and f-d transitions of Gd3+ and Tb3+, charge transfer of O2--Gd3+ and O2--Tb3+ were assigned. In Li6Gd(BO3)3:Tb3+, visible quantum cutting through downconversion was observed upon Tb3+ 4f8-4f75d1 excitation and host excitation. The quantum cutting process was demonstrated combining a possible model.
Co-reporter:Xuan Guo, Yuhua Wang, Jiachi Zhang
Journal of Crystal Growth (1 April 2009) Volume 311(Issue 8) pp:2409-2417
Publication Date(Web):1 April 2009
DOI:10.1016/j.jcrysgro.2009.02.006
A series of multicrystal and monocrystal samples of yttrium orthoborate YBO3:Eu with different morphologies and sizes were prepared by a simple hydrothermal (HT) method at a low temperature of 260 °C for 3 h, in the absence of any surfactant and template, without milling and post calcination. Samples are characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM). The morphologies and sizes of YBO3:Eu, most of which are prepared for the first time, include polycrystalline nano-sheet; monocrystalline nano-sheet, nano-particle, submicro-sheet, submicro-rod and submicro-tube; micro-flower and micro-downy ball, which are assembled by orderly nano-sheets. At the same time, multifarious clear and high-quality selected-area electron diffraction (SAED) patterns including multicrystal diffraction rings and monocrystal diffraction spots were obtained for the first time, which provide abundant stuff to study the crystal structure of YBO3. However, all the innermost diffraction rings or spots of SAED patterns cannot be indexed by the currently accepted hexagonal crystal structure of YBO3, whose space group is P63/m and lattice parameters are a=3.778 Å, c=8.810 Å. On the other hand, the whole diffraction pattern can be successfully indexed by another hexagonal structure, whose space group is P6¯c2 and lattice parameters are a=6.454 Å, c=8.810 Å. In addition, this structure is also supported by the XRD results. As a result, the crystal structure of YBO3 is clarified.
Co-reporter:Shuangyu Xin, Yuhua Wang, Pengyu Dong, Wei Zeng and Jia Zhang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 48) pp:NaN8160-8160
Publication Date(Web):2013/10/23
DOI:10.1039/C3TC31356E
CaAl2O4:Eu2+, Nd3+ nanofibers were prepared via the electrospinning process by using core–sheath CaAl2O4:Eu2+, Nd3+/carbon nanofibers as templates, combined with a subsequent annealing treatment. The obtained nanofibers are smooth with tunable diameters ranging from 50 to 120 nm by simply changing the ratio of inorganic precursors to solvent. The intermediate state is composed of hollow CaAl2O4:Eu2+, Nd3+@carbon nanofibers. The formation process, luminescent properties and long lasting performance are investigated. This facile method for synthesizing nanofibers may have potential applications in the field of in vivo imaging and coatings for long lasting phosphors.
Co-reporter:Jia Zhang, Yuhua Wang, Zhigang Xu, Haixia Zhang, Pengyu Dong, Linna Guo, Fenghua Li, Shuangyu Xin and Wei Zeng
Journal of Materials Chemistry A 2013 - vol. 1(Issue 3) pp:NaN338-338
Publication Date(Web):2012/10/30
DOI:10.1039/C2TB00045H
In this paper, size-controlled morphologies of (Y, Gd)VO4 and (Y, Gd)VO4:Ln3+ (Ln = Eu, Yb, Er, and Ho) were obtained via a facile hydrothermal route, and their properties for drug delivery and photoluminescence were investigated. Monodisperse ellipsoid-like hollow (Y, Gd)VO4 were designed by employing (Y, Gd)(OH)CO3 colloidal spheres as a sacrificial template and NH4VO3 as a vanadium source, and the formation mechanism could be interpreted by the Kirkendall effect. The control of particle size for hollow (Y, Gd)VO4 was realized, facilitating their practical application. Mesoporous core–shell structured (Y, Gd)VO4:Ln3+@nSiO2@mSiO2 were designed to improve the properties for drug release. Typically, red emission of YVO4:Eu3+ predominated under 465 nm excitation; the upconversion spectra of YVO4:Yb3+, Er3+ and YVO4:Yb3+, Ho3+ revealed green and red color upon 980 nm excitation, respectively. The biocompatibility and drug release evaluations indicate the potential biological applications of the samples.
Co-reporter:Xufeng Zhou, Zhiya Zhang and Yuhua Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 15) pp:NaN3683-3683
Publication Date(Web):2015/02/17
DOI:10.1039/C4TC02807D
A new silicate phosphor MgGd4Si3O13:Ce3+,Tb3+ was successfully synthesized with the objective of application in ultraviolet-excited light emitting diodes (LEDs) and field emission displays (FEDs). The structural and photoluminescence (PL) properties of un-doped MgGd4Si3O13 were studied. The PL properties and the energy transfer from Gd3+ to Tb3+ and Ce3+ to Tb3+ in Ce3+ and Tb3+ singly- and co-doped MgGd4Si3O13 were discussed. Ce3+ occupying two different crystalline sites show diverse PL properties and distinct energy transfer efficiencies to Tb3+. The cathodoluminescence (CL) spectra, depending on the accelerating voltage and probe current, were also studied. Excellent degradation resistance properties with good colour stability were obtained with continuous low-voltage electron-beam excitation.
Co-reporter:Bitao Liu, Yongji Huang, Yan Wen, Luojun Du, Wei Zeng, Yurong Shi, Feng Zhang, Ge Zhu, Xuhui Xu and Yuhua Wang
Journal of Materials Chemistry A 2012 - vol. 22(Issue 15) pp:NaN7491-7491
Publication Date(Web):2012/03/09
DOI:10.1039/C2JM16114A
A series of composites of nanocrystalline TiO2 with exposed {001} facets and high quality graphene sheets (GS) were synthesized via a one-step hydrothermal reaction in an ethanol–water solvent. The obtained {001} facets-exposed TiO2/GS photocatalysts were characterized by Raman spectroscopy (RS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction pattern (XRD), field emission scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet visible (UV-vis) diffuse reflectance spectroscopy (DRS) and Electrical Impedance Spectroscopy (EIS). They showed a better photocatalyst properties than P25 and other normal TiO2/GS composites, which could be explained on the basis of the formation of chemical Ti–O–C bond and the formation of nano-sized Schottky interfaces at the contacts between TiO2 and GS. The influence of the exposed {001} facets on the photocatalytic activity was investigated. The result showed that positively charged dye molecules are preferentially adsorbed onto the TiO2/GS composites due to the photogenerated charge gathered on GS. Overall, this work could provide new insights into the fabrication of TiO2–carbon composites as high performance photocatalysts and facilitate their application in addressing environmental protection issues.
Co-reporter:Yurong Shi, Yan Wen, Meidan Que, Ge Zhu and Yuhua Wang
Dalton Transactions 2014 - vol. 43(Issue 6) pp:NaN2423-2423
Publication Date(Web):2013/10/31
DOI:10.1039/C3DT52405A
A rare-earth free red emitting β-Zn3B2O6:Mn2+ phosphor was prepared by a solid-state reaction method. The crystal structure, photoluminescent and cathodoluminescent properties of β-Zn3B2O6:Mn2+ were systematically investigated. The absorption and photoluminescence excitation spectra confirm that β-Zn3B2O6:Mn2+ matches the UV LED chip. Under UV light and low-voltage electron beam excitations, an interesting orange-red emission band centered at ∼600 nm of Mn2+ at the tetrahedral Zn2+ sites is observed. Besides, the unusual red shift with increasing Mn2+ content is also found and contributed to an exchange interaction between Mn2+. In addition, under low-voltage excitation, β-Zn3B2O6:Mn2+ exhibits higher color purity of 98.1% than that of the commercial ZnS:Ag,Cd yellow phosphor and reported ZnGeN2:Mn2+ orange phosphor, which indicated the β-Zn3B2O6:Mn2+ has a patenting application in FEDs.
Co-reporter:Wei Zeng, Yuhua Wang, Shaochun Han, Wenbo Chen, Gen Li, Yanzhao Wang and Yan Wen
Journal of Materials Chemistry A 2013 - vol. 1(Issue 17) pp:NaN3011-3011
Publication Date(Web):2013/03/12
DOI:10.1039/C3TC30182F
A novel yellow emitting long-persistent phosphor Ca2BO3Cl:Eu2+,Dy3+ is developed. The incorporation of Dy3+ ions, which act as trap centers, largely extends the thermoluminescence characteristics and evidently enhances the persistent luminescence behavior of the phosphor. Both fluorescence and phosphorescence spectra of Ca2BO3Cl:Eu2+,Dy3+ reveal only one asymmetric broad emission band located at 580 nm, ascribed to the 5d–4f transitions of Eu2+ ions in two different sites. With the optimum doping concentration and sufficient excitation with UV light, the afterglow of samples can persist over 48 h above the recognizable intensity level (≥0.32 mcd m−2), a phenomenon that is infrequent and excellent. Furthermore, Ca2BO3Cl possesses an indirect bandgap of about 5.1 eV. Detailed processes and possible mechanism are studied and discussed.
Co-reporter:Ge Zhu, Zhipeng Ci, Qian Wang, Yan Wen, Shaochun Han, Yurong Shi, Shuangyu Xin and Yuhua Wang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 29) pp:NaN4496-4496
Publication Date(Web):2013/05/13
DOI:10.1039/C3TC30601A
A simple but effective strategy was introduced to realize color tunability of a composite phosphor Y2SiO5:Ce/Y3Al5O12:Ce (YSO:Ce/YAG:Ce). The main idea was to use the cathodoluminescence of the YSO:Ce phosphor to additionally pump the photoluminescence of the YAG:Ce phosphor based on radiative energy transfer. Morphology as well as the cathodoluminescence properties of the YSO:Ce/YAG:Ce phosphors were investigated in detail. According to radiative energy transfer, an intense yellow emission with excellent cathodoluminescence properties can be obtained from YSO:Ce/YAG:Ce phosphors under low voltage electron beam excitation. Moreover, the emission color of the composite phosphors can be tuned from yellow to blue through adjusting the YSO:Ce content. The mechanism for the enhanced yellow emission and the color tunability were also discussed. It was experimentally proved that the color gamut and display hue could be greatly enriched and enhanced when employing the YSO:Ce/YAG:Ce composite phosphor as an additional phosphor for the typical tricolor FED phosphors.
Co-reporter:Quansheng Wu, Yuhua Wang, Zhigang Yang, Meidan Que, Yanyan Li and Chuang Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 5) pp:NaN834-834
Publication Date(Web):2013/10/30
DOI:10.1039/C3TC31471E
Pure nitride Ca-α-sialon phosphors with the composition Ca1.4−xAl2.8Si9.2N16:xEu (x = 0–0.3) were successfully prepared by gas-pressed sintering and their luminescence properties and morphology were investigated. Simultaneously, their time-resolved spectra were also presented. Ca1.4Al2.8Si9.2N16:Eu exhibited broad-band yellow-orange emission centered at ∼592 nm (FWHM ≈ 85 nm) under 400 nm excitation and with good thermal stability. Its emission intensity at 250 °C remained 88% of that measured at room temperature. The emission intensity was 1.7 times that of YAG:Ce3+ (P46-Y3) commercial phosphor. The outstanding luminescent properties allow it to be an attractive luminescent material for white LEDs.
Co-reporter:Xin Ding, Ge Zhu, Wanying Geng, Masayoshi Mikami and Yuhua Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 26) pp:NaN6685-6685
Publication Date(Web):2015/05/21
DOI:10.1039/C5TC01123J
The structural properties of wadeite (K2ZrSi3O9) have been investigated using high-resolution transmission electron microscopy and X-ray powder diffraction refinement, and the luminescence properties of Eu2+ activated K2ZrSi3O9 have been studied to explore new material for phosphor-converted white light near-ultraviolet light-emitting diodes (NUV-LEDs). Eu2+ was introduced into the K2ZrSi3O9 host in a reducing atmosphere, and the special crystallographic positions of Eu2+ were determined based on XRD, photoluminescence emission spectra, temperature dependence properties, and time-resolved photoluminescence. The calculated band gap is about 4.7 eV. The CIE chromaticity coordinates and FWHM of the blue phosphor K2ZrSi3O9:1%Eu2+ are (0.1538, 0.1857) and 57 nm respectively. The photoluminescence properties of co-doped Eu2+–Al3+and Eu2+–Sc3+ charge compensation pair phosphors were investigated. The Eu2+ single-doped K2ZrSi3O9 phosphor shows blue emission with a broad band peaking at 465 nm upon 400 nm NUV excitation. With Eu2+–Al3+ as the charge compensation pair, the photoluminescence properties do not change distinctly, while the photoluminescence emission spectrum red shifts by about 39 nm and the emission becomes green with the Eu2+–Sc3+ pair. Different occupation locations of the different charge compensation pairs were discussed. Blue and green emissions can be obtained from K2ZrSi3O9:Eu2+ compounds by different charge compensation mechanisms. This reveals that K2ZrSi3O9:Eu2+ possesses remarkable optical properties and can be used in NUV-LEDs.
Co-reporter:Yanyan Li, Jianyan Ding, Quansheng Wu, Qiang Long, Xicheng Wang and Yuhua Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 34) pp:NaN8955-8955
Publication Date(Web):2015/07/29
DOI:10.1039/C5TC01276G
A near-ultraviolet (near-UV) excited phosphor, Ca15Si20O10N30:Ce3+, was synthesized by a solid state reaction, and its crystal structure and luminescence properties were investigated in detail. Ca15Si20O10N30 crystallizes in a cubic unit cell with the space group Pa and the lattice parameters are determined to be a = b = c = 15.4195(3) Å. The maximum emission wavelength can be tuned from about 470 to 520 nm as the content of Ce3+ increases due to the energy transfer between various Ce3+ activators located in different coordination environments, which was verified by the time-resolved emission spectroscopy (TRES) and the variation in the decay rate with respect to the detection wavelength. Upon excitation at 365 nm, Ca15Si20O10N30:Ce3+ exhibited a relatively low thermal quenching, and the T50 is measured to be 233 °C. The above results indicate that Ca15Si20O10N30:Ce3+ is a promising candidate for application in white light-emitting diodes (LEDs).
Co-reporter:Xicheng Wang, Zhengyan Zhao, Quansheng Wu, Chuang Wang, Qian Wang, Li Yanyan and Yuhua Wang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 37) pp:NaN8801-8801
Publication Date(Web):2016/08/24
DOI:10.1039/C6TC01049K
A novel blue-emitting phosphor Na3Sc2(PO4)3:Eu2+ was successfully synthesized by solid-state reaction. The crystal structure, bandgap, and photoluminescence properties were investigated in detail. Under n-UV excitation, the NSP:Eu2+ phosphor exhibits a narrow blue emission peaking at 458 nm with a FWHM of about 50 nm. The concentration quenching mechanism of the NSP:Eu2+ is dominated by the dipole–dipole interaction. Moreover, the NSP:Eu2+ shows better PL intensity, colour purity and thermal quenching properties compared to the commercial BAM phosphor. Non-equivalence replacement of Eu2+ ions for Na+ ions causing defects, inducing the abnormal thermal quenching behaviour. All these results suggest that the NSP:Eu2+ phosphor can be a potential candidate for n-UV LED applications.
Co-reporter:Haijie Guo, Yuhua Wang, Wenbo Chen, Wei Zeng, Shaochun Han, Gen Li and Yanyan Li
Journal of Materials Chemistry A 2015 - vol. 3(Issue 42) pp:NaN11218-11218
Publication Date(Web):2015/09/28
DOI:10.1039/C5TC02283E
Thermoluminescence (TL) glow curves of Ca6BaP4O17:Eu2+,R3+ (R = Dy, Tb, Ce, Gd, Nd) samples were measured above room temperature in order to compare the trap distributions in the band gap. The observed phenomenon indicates that R3+ ions (R = Dy, Tb, Ce, Gd, Nd) have different effects on the trap properties of the Ca6BaP4O17:Eu2+ phosphor. The most shallow trap (0.620 eV) for the Tb3+ ion and the deepest trap (0.762 eV) for the Dy3+ ion eventually led to shorter duration (4.3 h and 1.2 h, respectively), while the appropriate trap depth (0.716 eV) for the Nd3+ ion makes the Ca6BaP4O17:Eu2+,Nd3+ sample show the longest afterglow duration (37.9 h). Codoping the Tb3+ ion slightly increases the instinct traps of the Ca6BaP4O17:Eu2+ sample and creates a new low-temperature TL peak corresponding to a relatively shallow trap leading to the strongest initial afterglow brightness (0.887 cd m−2), while codoping with other R3+ ions (R = Dy, Ce, Gd, Nd) creates new appropriate or inappropriate traps. By recording a series of long-lasting phosphorescence (LLP) spectra with various irradiated times and TL experiments with varying delay time after ceasing the UV irradiation, the trap distribution of the depth and shape was evaluated. The result provides a better understanding of the role of these trapping centers played in the persistent luminescence mechanism.
Co-reporter:Shanshan Du, Deyin Wang, Qinping Qiang, Xinlong Ma, Zuobin Tang and Yuhua Wang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 29) pp:NaN7155-7155
Publication Date(Web):2016/07/05
DOI:10.1039/C6TC01812B
Micro-sized Gd6O5F8 particles doped with Yb3+, Ho3+ and Li+ ions have been synthesized by a facile hydrothermal route. The dual-model up- and down-conversion luminescence was investigated under visible blue (VIS-B) light (451 nm) and near infrared (NIR) light (980 nm) excitations. The structural properties of the products are analysed by X-ray diffraction (XRD). Upon excitation to the 2F5/2 level of Yb3+ using a 980 nm laser diode, Gd6O5F8:Yb3+,Ho3+ exhibits intense up-converted green and red emission at 545 nm and 660 nm, which correspond to the 5S2 → 5I8 and 5F5 → 5I8 transitions of Ho3+, respectively. The nearly quadratic dependence of the green/red emission intensity on the excitation power indicates that a two-photon up-conversion process was involved to populate the green (5S2) and red levels (5F5) of Ho3+. In contrast, upon excitation Ho3+ to its 5F1 level by 451 nm blue light, both visible and near-infrared emissions peaking at 545 nm, 660 nm, 980 nm and 1191 nm are simultaneously observed in the emission spectra, which are assigned to the 5S2 → 5I8 (Ho3+), 5F5 → 5I8 (Ho3+), 2F5/2 → 2F7/2 (Yb3+) and 5I6 → 5I8 (Ho3+) transitions, respectively. Meanwhile, the emission intensities of the up-converted green emission and down-converted emissions were further enhanced by co-doping Li+, which can be confirmed by the fact that the emission intensities of the up-converted green emission and down-converted NIR emission were increased 50% and 90% after co-doping 7% Li+. The energy transfer processes between Ho3+ and Yb3+ ions and the mechanisms of Li+ doping for the emission enhancement have been investigated and discussed. Additionally, the time-resolved luminescence traces are measured, and the luminescence lifetimes of the Ho3+ ions are calculated. Furthermore, the temperature-dependent up-conversion and down-shifted luminescence of Gd6O5F8:Yb3+,Ho3+,Li+ are investigated, and the results show that the ratio of up-converted green to red emission as well as the ratio of down-shifted green to blue emission in Gd6O5F8:Yb3+,Ho3+,Li+ all respond single exponentially to temperature, which could be applied to sense temperature.
Co-reporter:Zuobin Tang, Deyin Wang, Waheed U. Khan, Shanshan Du, Xicheng Wang and Yuhua Wang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 23) pp:NaN5313-5313
Publication Date(Web):2016/04/29
DOI:10.1039/C6TC01449F
A novel blue-emitting zirconium silicate phosphor K2ZrSi2O7:Eu2+ was prepared by solid-state reaction for the first time, and its crystal structure was determined from the XRD profiles by using Rietveld refinement and high-resolution transmission electron microscopy (HRTEM). The photoluminescence properties were investigated for the possible application in white light-emitting diodes (LEDs). The excitation spectra of the Eu2+ doped K2ZrSi2O7 phosphor show broad band excitation in the 250–410 nm region, and upon excitation at 350 nm, this phosphor showed a strong blue emission centered at 462 nm (full-width at half-maximum (FWHM) ∼ 70 nm). The thermal stability can be enhanced significantly by solid solution. The cathodoluminescence properties of K2ZrSi2O7:Eu2+ were also studied. Under continuous low-voltage electron bombardment, the phosphors display excellent degradation resistance and good color stability. A white LED fabricated with this phosphor and yellow-orange emitting phosphor Sr3SiO5:Eu2+ on a LED chip (λmax = 375 nm) was discussed. Driven by a 350 mA forward bias current, the fabricated lamp gives intense white light with a higher color rendering index of 86. All the results indicate that this phosphor has potential application in LEDs and FEDs.
Co-reporter:Qiang Long, Chuang Wang, Jianyan Ding, Yanyan Li, Quansheng Wu and Yuhua Wang
Dalton Transactions 2015 - vol. 44(Issue 32) pp:NaN14513-14513
Publication Date(Web):2015/07/10
DOI:10.1039/C5DT02368H
A near-UV excited phosphor, LiSr4(BN2)3:Eu2+ (LSBN:Eu2+), was synthesized using a solid-state reaction at 800 °C. The crystal structure of LSBN had been refined and determined from the XRD profiles by the Rietveld refinement method, which belongs to the space group Imm with the lattice constants a = b = c = 7.46112(23) Å. The excitation spectra of the LSBN:Eu2+ phosphors were centered at around 370 nm and covered the range from 300 to 450 nm. Under 400 nm excitation, the emission spectra of the LSBN:Eu2+ phosphors show a red emission centered at about 640 nm (FWHM ≈ 130 nm). And the energy transfer between the Eu2+ ions is confirmed to arise from the electric dipole–dipole interactions. The nontypical emission blue-shift in the single luminescence center with increasing temperature luminescence properties is also investigated. The results indicate that LSBN:Eu2+ could be conducive to the development of white light emitting diodes.
Co-reporter:Jia Zhang, Yuhua Wang, Linna Guo and Pengyu Dong
Dalton Transactions 2013 - vol. 42(Issue 10) pp:NaN3551-3551
Publication Date(Web):2012/11/28
DOI:10.1039/C2DT32463F
Monodisperse and uniform Y6O5F8:RE3+ (RE = Yb, Er, and Ho) microarchitectures with various morphologies have been constructed by a facile surfactant-assisted hydrothermal route, and their up-conversion luminescence and NIR quantum cutting properties were investigated. Hollow hexagonal prisms, microbundle gatherings by rods, and solid hexagonal prisms were designed by employing CTAB, PVP, and EDTA as additives, respectively. Under 980 nm excitation, the Y5.34O5F8:0.6Yb3+, 0.06Er3+ samples obtained using different additives exhibit similar emission spectra profiles with predominating peaks at 670 nm; the Y5.34O5F8:0.6Yb3+, 0.06Ho3+ samples give green emissions with the strongest peaks around 544 nm. The NIR quantum cutting for the Y6O5F8:Yb3+, Ho3+ samples was identified by the NIR emission spectra upon both 360 and 450 nm excitation. The corresponding quantum cutting mechanisms were discussed through the energy level diagrams, in which a back-energy-transfer from Yb3+ to Ho3+ was first proposed to interpret the spectral characteristics. A modified calculation equation for the quantum efficiency of Yb3+–Ho3+ coupled by exciting at 450 nm was suggested according to the quantum cutting mechanism. The efficient NIR luminescence and quantum cutting in Yb3+, Ho3+ co-doped Y6O5F8 reveal a possible application in modifying the solar spectrum to enhance the efficiency of silicon solar cells.
Co-reporter:Gen Li, Yuhua Wang, Wei Zeng, Wenbo Chen, Shaochun Han, Haijie Guo and Xicheng Wang
Dalton Transactions 2015 - vol. 44(Issue 40) pp:NaN17578-17578
Publication Date(Web):2015/09/10
DOI:10.1039/C5DT02748A
A novel green afterglow phosphor NaBaScSi2O7:Eu2+ was prepared by a solid state reaction under a reductive atmosphere. The NaBaScSi2O7:Eu2+ phosphor shows two emission bands centered at about 424 (weak) and 502 nm (strong) due to the substitution of Eu2+ in both Ba+ and Na2+ sites, and energy transfer from EuBa (424 nm) to EuNa (502 nm) was found. Both EuBa and EuNa contribute to the afterglow process while EuNa dominates. Na0.99BaScSi2O7:0.01Eu2+ exhibits green long lasting phosphorescence, whose duration is more than 1 h. The thermoluminescence properties of NaBaScSi2O7:Eu2+ and the relationship between thermoluminescence and thermal quenching properties were discussed in detail. This work provides a new and efficient candidate for long lasting phosphorescence materials.
Co-reporter:Pengyu Dong, Yuhua Wang, Huihui Li, Hao Li, Xinlong Ma and Lili Han
Journal of Materials Chemistry A 2013 - vol. 1(Issue 15) pp:NaN4656-4656
Publication Date(Web):2013/02/20
DOI:10.1039/C3TA00130J
A novel and facile soft-chemical method has been proposed for the synthesis of Ag3PO4 crystals with various new morphologies (branch, tetrapod, nanorod, triangular prism), and the morphological effect on the photocatalytic activity of the obtained Ag3PO4 crystals has been investigated. It is demonstrated that the morphology of Ag3PO4 crystals can be controlled by simply adjusting external experimental conditions such as static and ultrasonic conditions. Photocatalytic results indicate that the branched Ag3PO4 crystal with porous structure shows the highest photocatalytic activity among these Ag3PO4 crystals with multiform morphologies, and the photocatalytic rate constants of branched Ag3PO4 are 2.8 and 4 times those of irregular spherical Ag3PO4 for degradation of methylene blue (MB) and rhodamine B (RhB) dye solutions under visible light irradiation, respectively.
Co-reporter:Linna Guo, Yuhua Wang, Lili Han, Qinping Qiang, Wei Zeng, Zehua Zou, Bing Wang and Xiaoxia Guo
Journal of Materials Chemistry A 2013 - vol. 1(Issue 47) pp:NaN7962-7962
Publication Date(Web):2013/10/17
DOI:10.1039/C3TC31838A
In the present paper, the band structure and density of states of Lu6O5F8 were primarily studied with the help of first-principles calculations, and the indirect band gap of Lu6O5F8 is estimated to be 4.13 eV wide. Lu(OH)1.57F1.43/NH4Lu2F7/Lu6O5F8 nano/microcrystals with diverse morphologies, sizes and dimensions have been synthesized via a mild and controllable hydrothermal process using citric acid trisodium salt dehydrate (Cit3−), hexadecyltrimethylammonium bromide (CTAB), ethylenediaminetetraacetic acid (EDTA), ethylenediaminetetraacetic acid disodium salt (EDTA2−), sodium dodecyl benzene sulfonate (SDBS), ethylenediamine (EA) or polyvinylpyrrolidone (PVP), etc. as an additive, respectively. The phases, morphologies, sizes, and luminescence properties of the as-prepared samples were well characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL) and cathodoluminescence (CL) spectroscopy, respectively. The results indicate that the phase, morphology, and size of Lu(OH)1.57F1.43/Lu6O5F8 can be tuned in a controlled manner by altering the amount or kinds of additives, the pH values of the initial solution, and the reaction time. Furthermore, the time-dependent morphology evolution shows that the resulting microrods, hexagonal prisms, flower clusters and spheres were synthesized by a dissolution–reconstruction formation mechanism. It is expected that the synthetic strategy can be extended to controllable synthesis of other types of nano/microcrystals as well. Upon ultraviolet (UV), vacuum ultraviolet (VUV) and electron beam excitation, the luminescence properties as well as the emission mechanisms of the Ln3+ (Ln = Eu/Tb/Ce/Dy) single doped precursor (NH4Lu2F7, Lu(OH)1.57F1.43) and final product (Lu6O5F8) are all compared and studied. All in all, the multifunctional Ln3+ doped NH4Lu2F7/Lu(OH)1.57F1.43/Lu6O5F8 nano/microcrystals have potential applications in photoluminescence areas and field emission display devices.
Co-reporter:Quansheng Wu, Xicheng Wang, Zhengyan Zhao, Chuang Wang, Yanyan Li, Aijun Mao and Yuhua Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 37) pp:NaN7738-7738
Publication Date(Web):2014/07/23
DOI:10.1039/C4TC01131G
A green-emitting nitride phosphor Ca1.4Al2.8Si9.2N16:Ce3+, Li+ (CASN:Ce) has been successfully synthesized which is applicable to near-ultraviolet based light-emitting diodes (LEDs) and field emission displays (FEDs). The characteristic photoluminescence (PL) properties were studied in detail by PL excitation, emission spectra and time-resolved spectroscopy. CASN:0.10Ce exhibits broad-band green emission centered at ∼525 nm (FWHM ≈ 135 nm) under 395 nm excitation and with excellent thermal stability. The effect of host lattice composition on PL properties was also discussed. The cathodoluminescence (CL) spectra as a function of accelerating voltage and probe current were also studied. Excellent degradation resistance properties with good color stability were obtained by continuous low-voltage electron-beam excitation of the phosphor.
Co-reporter:Xicheng Wang, Takatoshi Seto, Zhengyan Zhao, Yanyan Li, Quansheng Wu, Hao Li and Yuhua Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 22) pp:NaN4481-4481
Publication Date(Web):2014/03/25
DOI:10.1039/C4TC00190G
A series of quaternary nitride solid solutions with a general formula of Sr1−xCaxYSi4N7:Eu2+ (1 atom%) were synthesized by the carbothermal reduction and nitridation (CRN) method. The XRD patterns confirm the formation of a solid solution of Sr1−xCaxYSi4N7:Eu2+ (0 ≤ x ≤ 0.5). With an increase in x, the emission spectra shift from 540 nm to 564 nm under n-UV excitation. In addition, the temperature dependence of the PL intensity was investigated. The thermal stability is comparable to that of the commercial (Ba,Sr)2SiO4:Eu2+ phosphor. All the results indicate that the solid solution Sr1−xCaxYSi4N7:Eu2+ can be a good candidate of phosphor applicable to n-UV LEDs for solid-state lighting.
Co-reporter:Zhengyan Zhao, Zhigang Yang, Yurong Shi, Chuang Wang, Bitao Liu, Ge Zhu and Yuhua Wang
Journal of Materials Chemistry A 2013 - vol. 1(Issue 7) pp:NaN1412-1412
Publication Date(Web):2013/01/07
DOI:10.1039/C2TC00732K
A novel red-emitting oxonitridosilicate phosphors, Sr2SiNzO4−1.5z:Eu2+ (0.7 < z < 1.2), was prepared by solid state reaction in NH3–N2 atmosphere. The crystal structure was determined by Rietveld analysis on powder X-ray data. Sr2SiNzO4−1.5z (0.7 < z < 1.2) crystallizes in an orthorhombic structure with the space group of Pmnb: ba−c (no. 62), and cell parameter a = 5.67366(5) Å, b = 7.09777(4) Å, c = 9.75112(1) Å. Sr2SiNzO4−1.5z:Eu2+ (0.7 < z < 1.2) exhibited broad-band red emission centred at ∼620 nm (FWHM ≈ 95 nm) under blue light irradiation with a high QE value of 78.0% and good thermal stability, its emission intensity remains 87% at 150 °C of that measured at room temperature. The outstanding luminescent properties allow it to be an attractive red luminescent material for white LEDs.
Co-reporter:Linna Guo, Yuhua Wang, Zehua Zou, Bing Wang, Xiaoxia Guo, Lili Han and Wei Zeng
Journal of Materials Chemistry A 2014 - vol. 2(Issue 15) pp:NaN2772-2772
Publication Date(Web):2014/01/28
DOI:10.1039/C3TC32540G
A series of ErF3 samples with different morphologies (flake, truncated octahedral, flower-like and rice-like microcrystals) and sizes (20 nm–2 μm) were prepared by an aqueous-based hydrothermal and coprecipitation route, respectively. The crystal structure of ErF3 is firstly established via the Rietveld refinement result of the powder XRD data. In addition, the ErF3 matrix without doping sensitizer or activator shows bright red upconversion emission under excitation at 980 nm. It is worthwhile pointing out that ErF3 with an octahedral morphology demonstrates the highest relative intensity, with that of flower-like microcrystals following, but the nanoflakes show the lowest intensity, and the relative intensity is almost 8 times as low as that of the microcrystals. Further doping with Li+ would enhance the upconversion luminescence intensity, and the upconversion emission intensity of the optimal sample with doping 6 mol% Li+ is four times stronger than that of a Li+ free sample. Furthermore, upon electron beam excitation, the cathodoluminescence properties of a ErF3 matrix as a new upconversion host are also studied, which is an interesting phenomenon.
Co-reporter:Jianyan Ding, Yanyan Li, Quansheng Wu, Qiang Long, Chuang Wang and Yuhua Wang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 33) pp:NaN8549-8549
Publication Date(Web):2015/07/14
DOI:10.1039/C5TC01508A
In this work, a broad excitation band of Li2SiN2:Eu3+ with the peak at 357 nm has been found and investigated. The photoluminescence, morphologies and thermal stability of the samples were also measured. Under excitation at 357 nm and 300 nm, sharp red and green light can be observed due to the 5D0–7F2 transition of the Eu3+ ions and the 5D4–7F5 transition of the Tb3+ ions, respectively. According to the Diffuse reflectance spectra in combination with the energy level diagram of Li2SiN2:0.02Eu3+, we deduced that the broad excitation bands belong to the charge transfer band (CTB), which have also been observed in Li2SiN2:Tb3+ with the peak at 271 nm. And the thermal stabilities of the samples have been found to be connected with the CTB.
Co-reporter:Xin Ding and Yuhua Wang
Physical Chemistry Chemical Physics 2017 - vol. 19(Issue 3) pp:NaN2458-2458
Publication Date(Web):2016/12/14
DOI:10.1039/C6CP08300E
A novel apatite mineral of Ba5(PO4)2SiO4 was synthesized successfully using a traditional high temperature solid-state reaction. Its structure was determined by high-resolution transmission electron microscopy, fast Fourier transform, energy dispersive X-ray spectroscopy, and X-ray powder diffraction Rietveld refinement, and this was found to be a hexagonal crystal system with the space group attributed to P63/m (176). Moreover, a series of Eu2+ doped Ba5(PO4)2SiO4 phosphors were investigated. The photoluminescence (PL) properties of Ba5(PO4)2SiO4:Eu2+ were investigated in detail by density functional theory calculations, diffuse reflection spectra, emission–excitation spectra, decay curves, and temperature dependence spectra. It can emit green light peaking at ∼515 nm under 405 nm NUV excitation with quantum efficiency 31.89%. According to structure and photoluminescence (PL) property analysis, Eu2+ can occupy two kinds of Ba2+ site. The concentration quenching mechanism of Eu2+ could be a d–d interaction luminescence center. It has poor temperature stability properties because of too much temperature-dependent electron–phonon interaction at high temperature. Fabricated white-LEDs using a 405 nm GaN NUV chip combined with a blend of RGB phosphors: CaAlSiN3:Eu2+, Ba5(PO4)2SiO4:1%Eu2+ and BAM:Eu2+, driven by 30 mA current can get warm-white light with chromaticity coordinates (0.355, 0.342) and correlated color temperature (CCT) 4561 K. This demonstrates that Ba5(PO4)2SiO4:Eu2+ is a potential green phosphor matching NUV LED chips to get white light.
Co-reporter:Yaxin Cao, Jianyan Ding, Xin Ding, Xicheng Wang and Yuhua Wang
Journal of Materials Chemistry A 2017 - vol. 5(Issue 5) pp:NaN1194-1194
Publication Date(Web):2016/12/28
DOI:10.1039/C6TC04827G
Novel single-phase phosphors with the multi-cation-site Na2BaCa(PO4)2:Eu,xMn were synthesized by a traditional solid-state reaction method. The photoluminescence (PL) investigation indicated that the emitting light was tunable from blue to yellow with a variation in the Mn content and reaches a warm white with the CIE coordinate of (0.36, 0.32) and corresponding color temperature (CCT) of 4346 K when x is 0.07. The framework of the NBCP was compact, and the Ca2+ polyhedron is coplanar with the Ba2+ polyhedron one by one along the c axis, sharing 6 O2− ions on the edge. This is the reason for the excellent thermally stability of the phosphors, which keep more than 90% of the initial PL intensity under 150 °C. Based on these facts, NBCP:Eu,xMn has potential application as a white light emitting diode (WLED). Cathodoluminescence (CL) properties were also investigated, and the phosphor has considerable luminescence intensity and high current saturation intensity.
Co-reporter:Xicheng Wang, Zhengyan Zhao, Quansheng Wu, Yanyan Li and Yuhua Wang
Journal of Materials Chemistry A 2016 - vol. 4(Issue 48) pp:NaN11403-11403
Publication Date(Web):2016/10/26
DOI:10.1039/C6TC03933B
A novel garnet phosphor, Ca2LuHf2(AlO4)3:Ce3+ (CLHA:Ce3+), was successfully designed and synthesized using a solid-state method. Its crystal structure, band structure and photoluminescence properties were investigated in detail. Under n-UV excitation, CLHA:Ce3+ exhibited cyan to blue-green emission depending on the Ce3+ concentration. The QE of the optimal sample was 50.3%. The concentration quenching mechanism of the Ce3+ emission was dominated by dipole–dipole interactions. A novel method to obtain white light was developed by combining the CLHA:Ce3+ phosphor with a CaAlSiN3:Eu2+ red phosphor. Both the emission intensity and thermal stability of CLHA:Ce3+ were found to be superior to those of the commercial (Sr,Ba)2SiO4:Eu2+ phosphor. All of the results indicate the CLHA:Ce3+ phosphor to be a promising candidate for application in white LEDs.
Co-reporter:Xin Ding, Qian Wang and Yuhua Wang
Physical Chemistry Chemical Physics 2016 - vol. 18(Issue 11) pp:NaN8097-8097
Publication Date(Web):2016/02/16
DOI:10.1039/C6CP00168H
A series of novel K2Ge4O9:Mn4+ phosphors with red emission under blue light excitation have been synthesized successfully by traditional high-temperature solid-state reaction. The structure of K2Ge4O9 has been investigated by high-resolution transmission electron microscopy, scanning electron microscopy and X-ray powder diffraction with Rietveld refinement. The PL properties have been investigated by measuring diffuse reflection spectra, emission spectra, excitation spectra, decay curves and temperature-dependent spectra. The KGO:0.1% Mn4+ phosphor can emit red light peaking at 663 nm under UV or blue light excitation. The critical quenching concentration of Mn4+ was about 0.1 mol%. The concentration quenching mechanism could be a d–d interaction for the Mn4+ center. The CIE chromaticity coordinates and FWHM are (0.702, 0.296) and 20 nm, which demonstrated that the K2Ge4O9:Mn4+ has a high color purity. By tuning the weight ratio of yellow and red phosphors, the fabricated white LEDs, using a 455 nm InGaN blue chip combined with a blend of the yellow phosphor YAG:Ce3+ and the red-emitting KGO:Mn4+ phosphor driven by a 40 mA current, can get white light with chromaticity coordinates (0.405, 0.356) and CCT 3119 K. These results indicated that K2Ge4O9:Mn4+ is a potential red phosphor to match blue LED chips to get warm white light.
Co-reporter:Gen Li, Yuhua Wang, Wei Zeng, Wenbo Chen, Shaochun Han, Haijie Guo and Yanyan Li
Journal of Materials Chemistry A 2016 - vol. 4(Issue 15) pp:NaN3312-3312
Publication Date(Web):2016/03/10
DOI:10.1039/C5TC04396D
A series of novel Ce3+ singly doped and Ce3+/Tb3+ codoped color-tunable NaBaScSi2O7 phosphors were synthesized via the solid state method. The morphology, UV-vis reflectance, photoluminescence emission and excitation spectra, the lifetime and the thermal quenching properties were investigated in detail. NaBaScSi2O7:Ce3+ phosphors showed intense blue emission at about 425 nm, corresponding to the transitions from the lowest 5d excited state to the 2F5/2 and 2F7/2 spin orbit 4f ground states of Ce3+ ions, under optimal excitation of 349 nm. Under excitation of Ce3+ ions at 349 nm, the emission spectra of NaBaScSi2O7:Ce3+,Tb3+ phosphors consisted of a blue emission band of Ce3+ ions at 425 nm and a series of strong green emission lines at 488, 542, 582, and 625 nm due to the 5D4 → 7FJ (J = 6, 5, 4, and 3) characteristic transitions of Tb3+ ions. A possible energy transfer mechanism was proposed and ascribed to the dipole–dipole interaction on the basis of the experimental results and analysis. In addition, the cathodoluminescence properties of NaBaScSi2O7:Ce3+,Tb3+ were also studied in detail. The current results indicate that NaBaScSi2O7:Ce3+,Tb3+ can serve as a potential phosphor for application in UV-WLEDs and FEDs.
Co-reporter:Linna Guo, Yuhua Wang, Wei Zeng, Lei Zhao and Lili Han
Physical Chemistry Chemical Physics 2013 - vol. 15(Issue 34) pp:NaN14302-14302
Publication Date(Web):2013/06/25
DOI:10.1039/C3CP51816G
A series of GdF3:Yb3+, Ln3+ (Ln = Ho, Tm, Er, Pr, Tb) nanoparticles were prepared by a simple and green hydrothermal method without any additives, which exhibited an ellipse-like shape with a diameter of 63 nm and a length of 101 nm on average. To prove the existence (or not) of near infrared quantum cutting for various lanthanide ion couples (Yb/Ho; Yb/Tm; Yb/Er; Yb/Pr; Yb/Tb) in one host lattice (GdF3), the measured luminescence spectra and decay lifetimes of these samples were analysed. Furthermore, the band structures and densities of state of GdF3 were also studied with the help of first-principles calculations, and the direct band gap of GdF3 was estimated to be 7.443 eV wide. Based on this, detailed processes and possible mechanisms of the luminescence phenomena are discussed. GdF3:Yb3+, Ln3+ nanoparticles may have potential applications in modifying the solar spectrum to enhance the efficiency of silicon solar cells.
Co-reporter:Yurong Shi, Ge Zhu, Masayoshi Mikami, Yasuo Shimomura and Yuhua Wang
Dalton Transactions 2015 - vol. 44(Issue 4) pp:NaN1781-1781
Publication Date(Web):2014/11/24
DOI:10.1039/C4DT03144J
A novel Ce3+ activated Lu3MgAl3SiO12:Ce phosphor was synthesized and found to crystallize in the garnet structure. The crystal structure of the synthesized phosphor has been characterised by X-ray diffraction and Rietveld refinement. Both room and high temperature photoluminescence spectra are utilized to investigate the luminescence properties and crystal field splitting. The high temperature quenching of these phosphors and their quantum efficiency (QE) are also studied using both the prepared YAG:Ce and the commercial YAG:Ce phosphor named P46-y3 as the reference. Upon excitation with blue light, the composition-optimized Lu3MgAl3SiO12:Ce phosphor exhibited strong yellow light with a high QE of 81.2% and better thermal stability than that of the commercial phosphor. The results indicate that the Lu3MgAl3SiO12:Ce phosphor can serve as a candidate for blue chip LEDs.
Co-reporter:Haijie Guo, Yuhua Wang, Gen Li, Jie Liu, Peng Feng and Dongwei Liu
Journal of Materials Chemistry A 2017 - vol. 5(Issue 11) pp:NaN2851-2851
Publication Date(Web):2017/02/13
DOI:10.1039/C7TC00133A
We developed a novel long-lasting phosphorescence (LLP) material BaZrSi3O9:Eu2+,Pr3+. The crystal structure, electronic structure and photoluminescence of this phosphor have been investigated systematically. The highlight of this work is the admirable LLP performances of BaZrSi3O9:Eu2+,Pr3+, which could be observed by the naked eye for 15 hours in the dark after ceasing the irradiation source. Moreover, we have analyzed the reason why the BaZrSi3O9:Eu2+,Pr3+ phosphor has such excellent persistent luminescence by exploring the distribution of traps in BaZrSi3O9:Eu2+,Pr3+ with the help of thermoluminescence (TL) spectra. A series of the excitation duration, decay duration and temperature dependent TL experiments of BaZrSi3O9:Eu2+,Pr3+ were conducted, revealing the trapping and detrapping of electrons into and from the shallow traps through the conduction band and the deeper traps via the tunnelling process. According to the experimental results, the mechanism of the feasible persistent luminescence of BaZrSi3O9:Eu2+,Pr3+ was also proposed and illustrated in detail.
Co-reporter:Qinping Qiang, Wenbo Chen, Xinlong Ma and Yuhua Wang
Dalton Transactions 2015 - vol. 44(Issue 13) pp:NaN6248-6248
Publication Date(Web):2015/02/19
DOI:10.1039/C4DT03690E
A series of x mol% Yb3+, 1 mol% Ho3+/1 mol% Er3+ (0 ≤ x ≤ 25) codoped BaLiF3 microcrystals with different cubic morphologies and sizes (1.52 μm–3.83 μm) were synthesized by a facile surfactant-assisted hydrothermal-microemulsion approach for the first time. The crystalline structure of BaLiF3 was established via the Rietveld refinement result of the powder X-ray diffraction (XRD) data. In addition, the growth process of cubic BaLiF3 crystals and the influence of different synthesis conditions on the morphology were studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, in this paper we first investigated the upconversion luminescence (UCL) properties of new Er3+/Ho3+, Yb3+-codoped BaLiF3 microcrystals under 980 nm excitation. The characteristic emission of Er3+ and Ho3+ was obtained, respectively. The blue emission in BaLiF3:Yb3+, Ho3+ which was comparatively more difficult to discover was also observed and explained by the energy level diagram. It is worthwhile to point out that BaLiF3:Yb3+, Er3+ practically showed pure red upconversion (UC) emission under excitation at 980 nm and the reasons behind this behavior are presented and discussed.
Co-reporter:Quansheng Wu, Zhigang Yang, Zhengyan Zhao, Meidan Que, Xicheng Wang and Yuhua Wang
Journal of Materials Chemistry A 2014 - vol. 2(Issue 25) pp:NaN4973-4973
Publication Date(Web):2014/03/18
DOI:10.1039/C3TC32422B
A near-UV excited phosphor, Y4Si2O7N2:Ce3+, was synthesized using a solid-state reaction. The crystal structure and luminescence properties were studied. Y4Si2O7N2 crystallizes in a monoclinic unit cell with space group P21/c, lattice constants a = 7.5678(2) Å, b = 10.4529(1) Å, c = 10.7779(3) Å and β = 110.06°, and cell volume = 800.85(2) Å3. The crystal structure of Y4Si2O7N2, featuring Si(O,N)4 polyhedra, is provided, and there are four different Y3+ coordination environments with two different coordination numbers in the structure. Ce3+-doped Y4Si2O7N2 exhibited a broad emission band, and the maximum emission wavelength could be tuned from blue (λem = 450 nm) to green (λem = 515 nm) by increasing the concentration of Ce3+. The quantum efficiency was determined to be about 47%. The results show that Y4Si2O7N2:Ce3+ is a candidate for use as a conversion phosphor for near-UV white LED applications.
Co-reporter:Wenjin Xu, Ge Zhu, Xufeng Zhou and Yuhua Wang
Dalton Transactions 2015 - vol. 44(Issue 19) pp:NaN9250-9250
Publication Date(Web):2015/04/13
DOI:10.1039/C5DT00866B
A novel phosphate Ca9La(GeO4)0.75(PO4)6 was investigated to add to the family of phosphate phosphors and application in LEDs. In this work, the single phase red-emission Ce3+,Mn2+ co-doped phosphate Ca9La(GeO4)0.75(PO4)6 phosphor was synthesized by the solid-state reaction from both theoretical and practical points of view. The crystal structure was determined by Rietveld refinement and TEM. Its cell parameters are a = b = 10.4077605(2) Å, and c = 37.4714968(1) Å. The characteristic photoluminescence properties were studied in detail using photoluminescence excitation spectra, emission spectra, decay times and thermal quenching properties. Purple and red broad band emission from Ce3+ and Mn2+ was detected under excitation at 313 nm. According to this research, the Ca9La(GeO4)0.75(PO4)6:Ce3+,Mn2+ phosphor shows high thermal stability in the red-emission area. With the increase of the temperature, the intensity ratio of Mn2+ and Ce3+ emission rises rapidly and the purity of red-emission is improved. In order to reasonably explain this special phenomenon, an implicit mechanism between thermal quenching and energy transfer is proposed based on the configurational coordinate diagram. In addition, the mechanism could be helpful for understanding the thermal properties of multiple activators Ce3+ and Mn2+ co-doped phosphors as the reference.
Co-reporter:Yang Li, Wenjing Liu, Xicheng Wang, Ge Zhu, Chuang Wang and Yuhua Wang
Dalton Transactions 2015 - vol. 44(Issue 29) pp:NaN13203-13203
Publication Date(Web):2015/06/11
DOI:10.1039/C5DT01409C
A double substitution induced blue-emitting phosphor Ca(Mg0.8, Al0.2)(Si1.8, Al0.2)O6:Eu2+ (CMAS:Eu2+) was successfully synthesized by a solid-state reaction process, and its structure and luminescence properties were investigated in detail. The crystal structure and chemical composition of the CMAS matrix were analyzed and determined based on Rietveld refinements and Energy Dispersive Spectroscopy (EDS). The composition-optimized CMAS:Eu2+ exhibited a strong blue light, centered at 446 nm upon excitation at 365 nm with the Commission Internationale de L'Eclairage (CIE) coordinates of (0.144, 0.113). Under 380 nm excitation, the PL emission intensity area of the optimized phosphor was found to be 46.95% of that of the commercial BaMgAl10O17:Eu2+ (BAM:Eu2+) phosphor and the quantum efficiency of the phosphor is 41.32%. The temperature-dependent PL studies have been investigated which show the thermal stability of the CMAS:Eu2+ phosphor compared with that of the CaMgSi2O6:Eu2+ (CMS:Eu2+) phosphor.
Co-reporter:Jianyan Ding, Quansheng Wu, Yanyan Li, Qiang Long, Chuang Wang and Yuhua Wang
Dalton Transactions 2015 - vol. 44(Issue 20) pp:NaN9636-9636
Publication Date(Web):2015/04/08
DOI:10.1039/C5DT00907C
In this study, a series of novel single-phased white light-emitting phosphors, Sr(7.3−x/2−y/2)Ca(2.7−x/2−y/2)(PO4)6F2:xEu2+,yMn2+ (0 ≤ x ≤ 0.06, 0 ≤ y ≤ 0.9) (SCPF:xEu2+,yMn2+), have been successfully prepared through a high temperature solid-state reaction. The crystal structure and photoluminescence have been measured and analyzed. The energy transfer mechanism is demonstrated to be a quadrupole–quadrupole interaction and the critical distance between the Eu2+ and Mn2+ has been calculated. Meanwhile, the efficiency η of the energy transfer from Eu2+ to Mn2+ can reach 76%. The excitation spectra monitored at 457 nm ranges from 290 nm to 400 nm. Under excitation at 365 nm, the emission spectra include two broad bands peaked at 458 nm and 570 nm. By changing the ratio of Eu2+/Mn2+, the emission color can change from blue to white. Furthermore, our results give the Commission International de L'Eclairage (CIE) chromaticity coordinates for the white LED as (0.334, 0.307) and a correlated color temperature of 3982 K, which indicates that the SCPF:Eu2+,Mn2+ phosphor is a very promising candidate for use as a near ultraviolet (NUV) white light-emitting diode (WLED) phosphor.
Co-reporter:Haijie Guo, Wenbo Chen, Wei Zeng, Gen Li, Yuhua Wang, Yanyan Li, Yang Li and Xin Ding
Journal of Materials Chemistry A 2015 - vol. 3(Issue 22) pp:NaN5850-5850
Publication Date(Web):2015/05/01
DOI:10.1039/C5TC00810G
A novel yellow-emitting long-lasting phosphate phosphor Ca6BaP4O17:Eu2+,Ho3+ is developed. The incorporation of Ho3+ ions, which act as trap centers, largely extends the thermoluminescence characteristics and evidently enhances the persistent luminescence behavior of the phosphor. Both the fluorescence and phosphorescence spectra of Ca6BaP4O17:0.02Eu2+,0.015Ho3+ reveal only one asymmetric broad emission band located at 553 nm, ascribed to the 5d–4f transitions of Eu2+ ions in two different Ca2+ sites. After 15 min of excitation, the initial long-lasting phosphorescence (LLP) intensity of Ca6BaP4O17:0.02Eu2+,0.015Ho3+ can reach about 0.13 cd m−2 and its LLP can last more than 47 h above the recognizable intensity level (0.32 mcd m−2), a phenomenon that is infrequent and excellent. Furthermore, the direct bandgap of about 4.081 eV for Ca6BaP4O17 provides a suitable bandgap for Eu2+ and Ho3+ ions. The results indicate that the phosphor has the potential to become a novel commercial LLP phosphor used in the field of emergency lighting and display. Detailed processes and a possible mechanism are studied and discussed.
Co-reporter:Shuangyu Xin, Yuhua Wang, Ge Zhu, Xin Ding, Wanying Geng and Qian Wang
Dalton Transactions 2015 - vol. 44(Issue 36) pp:NaN16106-16106
Publication Date(Web):2015/08/05
DOI:10.1039/C5DT02099A
A novel phosphate RbZnPO4 has been developed for the first time and the characteristic crystal structure of RbZnPO4 has been investigated in detail, based on the Fourier transform infrared reflection spectra and the structure refinement of X-ray diffraction data. After doping with Eu3+,RbZnPO4:Eu3+ shows distinctive deep red emission with dominating peaks at 596 and 701 nm. To provide a reasonable explanation for the relationship between photoluminescence and structure, the photoluminescence property has been discussed by analyzing the particular local ligand environment and site occupation of Eu3+ in RbZnPO4. More interestingly, temperature-sensitive emission behavior was found in RbZnPO4:Eu3+. Through the synthetical analysis of the configurational coordinate diagram, the charge compensation experiment and the CASTEP band structure calculation, a complex underlying mechanism is proposed to explain the abnormal temperature-sensitive emission behavior in RbZnPO4:Eu3+. The mechanism could be helpful for better understanding the thermal quenching process of Eu3+ in RbZnPO4 and also as a reference in some other temperature-sensitive phosphors.
Co-reporter:Xicheng Wang, Zhengyan Zhao, Quansheng Wu, Yanyan Li, Chuang Wang, Aijun Mao and Yuhua Wang
Dalton Transactions 2015 - vol. 44(Issue 24) pp:NaN11066-11066
Publication Date(Web):2015/05/01
DOI:10.1039/C5DT00800J
A series of SrSiAl2O3N2:Eu2+ (0.005 ≤ x ≤ 0.05) phosphors were successfully synthesized through a pressureless, facile, and efficient solid state route. The crystal structure, band structure, and their photoluminescence and cathodoluminescence properties were investigated in detail. The phosphors exhibit rod shape morphology with a uniform Eu2+ distribution. Under n-UV excitation the emission spectra shift from 477 to 497 nm with an increase of Eu2+ concentration. The concentration quenching mechanism of Eu2+ emission was dominated by the dipole–dipole interaction. The thermal stability is comparable to that of the commercial Ba2SiO4:Eu2+ phosphor. The phosphor also exhibits high current saturation and high resistance under low voltage electron bombardment. All the results indicate that the SrSiAl2O3N2:Eu2+ phosphors can be considered as candidates for application in both white LEDs and FEDs.
Co-reporter:Chuang Wang, Zhengyan Zhao, Quansheng Wu, Ge Zhu and Yuhua Wang
Dalton Transactions 2015 - vol. 44(Issue 22) pp:NaN10329-10329
Publication Date(Web):2015/04/27
DOI:10.1039/C5DT00815H
The promising green oxynitride phosphor, Ba3−xMgxSi6O12N2:Eu2+ was synthesized by the solid-state reaction method. The effect of Mg2+ doping on the structure and photoluminescence (PL) properties of Ba3Si6O12N2:Eu2+ was investigated systematically. The results reveal that the phosphor retains the single phase of Ba3Si6O12N2, with the lattice expanding upon increasing the Mg2+ concentration, in an appropriate range. This suggests that a large portion of Mg2+ enters into the interstitial sites of the crystal lattice. At a certain concentration, Mg2+ doping can greatly enhance the absorption and PL intensity and decrease the full widths at half maximum (FWHM) of Ba3Si6O12N2:Eu2+ phosphors. The green phosphor Ba2.87Eu0.1Mg0.03Si6O12N2 exhibited a small thermal quenching, which remained 82% of the initial emission intensity when measured at 150 °C. The quantum efficiency measured at 400 nm excitation was 38.5%. All the results indicate that the solid solution Ba3−xMgxSi6O12N2:Eu2+ can be a good candidate for phosphors applicable in n-UV LEDs for solid-state lighting.
Co-reporter:Qian Wang, Ge Zhu, Shuangyu Xin, Xin Ding, Ju Xu, Yuansheng Wang and Yuhua Wang
Physical Chemistry Chemical Physics 2015 - vol. 17(Issue 41) pp:NaN27299-27299
Publication Date(Web):2015/07/21
DOI:10.1039/C5CP02899J
A blue-emitting phosphor BaSc2Si3O10:Eu2+ was synthesized using the conventional solid-state reaction. The crystallographic occupancy of Eu2+ in the BaSc2Si3O10 matrix was studied based on the Rietveld refinement results and the photoluminescence properties. BaSc2Si3O10 exhibits blue emission ascribed to 3T2–1A1 and 3T1–1A1 charge transfer of SiO44− excited by 360 nm. All the phosphors of BaSc2Si3O10:Eu2+ exhibit strong broad absorption bands in the near ultraviolet range, and give abnormal blue emission upon 330 nm excitation. The abnormal phenomenon was explored in detail through many pieces of experimental evidence. The concentration of Eu2+ is optimized to be 3 mol% according to emission intensity and the quenching mechanism is verified to be a quadrupole–quadrupole interaction. The CIE coordinates of BaSc2Si3O10:0.03Eu2+ are calculated to be (0.15, 0.05) and BaSc2Si3O10:0.03Eu2+ shows similar thermal stability to commercial BaMgAl10O17:Eu2+.
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