Co-reporter:Li-Li Yu, Jun-Jie Zhu and Jing-Tai Zhao
Journal of Materials Chemistry A 2014 vol. 2(Issue 24) pp:9353-9360
Publication Date(Web):22 Apr 2014
DOI:10.1039/C4TA00155A
Hierarchical porous β-MnO2 nanoflowers self-assembled by ultrathin (thickness less than 10 nm) nanoplates have been successfully fabricated at room temperature. Because of its high specific surface area (267 m2 g−1) and proper pore size distributions (average pore size, ca. 5.9 nm), the obtained 3D nanomaterials achieve enhanced capacitance as high as 296.3 F g−1 at a scanning rate of 2 mV s−1, which is ∼20 times of those of the traditionally prepared nanostructural β-MnO2 (e.g. 1D hollow β-MnO2 nanorods with ∼14.9 F g−1). Furthermore, it has an appreciable ability to deliver large energy densities at high rates (67.4% capacitive retention). The comparable property with α-MnO2 indicates that such low-cost porous β-MnO2 nanoflowers may also be a very promising candidate material for supercapacitors besides lithium battery material.
Co-reporter:Zhi-Jun Zhang, Ang Feng, Xin-Yuan Sun, Kai Guo, Zhen-Yong Man, Jing-Tai Zhao
Journal of Alloys and Compounds 2014 Volume 592() pp:73-79
Publication Date(Web):15 April 2014
DOI:10.1016/j.jallcom.2013.12.211
•The direct band gap of CaZnOS is calculated to be 2.4 eV using the CASTEP mode.•CaZnOS:Ce3+ exhibits a broad band emission in the wavelength range of 450–650 nm.•The mechanism of luminescence and concentration quenching of Ce3+ have been investigated in detail.The electronic structure of CaZnOS calculated using the CASTEP mode is an intermediate band gap semiconductor with a direct band gap of 2.4 eV. Ce3+-activated CaZnOS samples were prepared by a solid-state reaction method at high temperature and their luminescence properties under UV–visible and X-ray excitation were investigated. CaZnOS:Ce3+ exhibits a broad band emission in the wavelength range of 450–650 nm, originating from the 5d–4f transition of Ce3+ for both under blue light (460 nm) and X-ray excitation. The mechanism of luminescence and concentration quenching of Ce3+ in CaZnOS have been investigated in detail. The results showed that the relative luminescence intensity reaches a maximum at 1 mol% of Ce3+, and the electric dipole–dipole interaction is the major mechanism for concentration quenching of Ce3+ emission in CaZnOS. The potential application of CaZnOS:Ce3+ has been pointed out.
Co-reporter:Li‐Hua Zheng, Xin‐Yuan Sun, Ri‐Hua Mao, Hao‐Hong Chen, Zhi‐Jun Zhang, Jing‐Tai Zhao
Journal of Non-Crystalline Solids 2014 Volume 403() pp:1-4
Publication Date(Web):1 November 2014
DOI:10.1016/j.jnoncrysol.2014.06.010
•High Li+ content Ce-doped Li2O–B2O3–P2O5 glasses were prepared at 865 °C.•Most of the glasses obtained are of high transparency, about 80% (2 mm thickness).•The UV excited photoluminescence decay time is about 28.5 ns.•X-ray excited luminescence shows boron anomaly phenomenon with the increase of B2O3.Ce3 +-doped lithium borophosphate glasses were prepared by melt quenching method, their luminescence properties were investigated by excitation and emission spectra, as well as X-ray excited luminescence (XEL) spectra. The broad emission band with the maximum center around 338 nm attributing to 5d–4f transitions of Ce3 + ions is observed, and the optimal concentration of CeO2 is found to be 0.75 wt.% in the CeO2-doped 57.5Li2O–5B2O3–37.5P2O5 scintillating glasses. Both the excitation and emission bands show a red shift in the 45Li2O–yB2O3–(55-y) P2O5–0.75 wt.% CeO2 glasses due to the increasing value of the optical basicity with the increase of y. Moreover, the strongest XEL intensity of 45Li2O–yB2O3–(55-y)P2O5–0.75 wt.% CeO2 glasses reaches a maximum at y = 16.5, which might be associated with the decreasing concentration of the non-bridging oxygen and the change ratio between BO4 groups and total amount of borate groups by increasing B2O3. From the standpoints of the high Li+ concentration and fast fluorescence decay time (28.5 ns), Ce3 +-doped lithium borophosphate glasses are potential candidates for neutron detection.
Co-reporter:Bi-Qiu Liu, Jiao Wang, Lin-Lin Zhu, Hui Zhang, Hao-Hong Chen, Fang-Fang Xu, Kai Guo, Jing-Tai Zhao
Materials Research Bulletin 2014 51() pp: 180-184
Publication Date(Web):
DOI:10.1016/j.materresbull.2013.11.057
Co-reporter:Li-Li Yu;Jun-Jie Zhu
European Journal of Inorganic Chemistry 2013 Volume 2013( Issue 21) pp:3719-3725
Publication Date(Web):
DOI:10.1002/ejic.201300265
Abstract
Mesoporous nanostructured α-manganese dioxide (MN-α-MnO2) powders in a sponge-like three-dimensional network have been successfully synthesized in high yields in a simple, template-free manner at room temperature. Its unique structure has been found to be related to the glucose solution rather than to the KMnO4 solution. A possible mechanism for the formation of MN-α-MnO2 by the oxidation of MnO2 precursors cross-linked by glucose networks is proposed that is supported by experimental results. The electrochemical studies showed that MN-α-MnO2 exhibits good electrochemical properties in 1 M Na2SO4 due to its high specific surface area (ca. 220 m2 g–1) and proper pore size distributions (ca. 5 nm), which indicates that it has potential for use as a high-performance supercapacitor due to its good electrochemical performance, low cost and environmental friendliness.
Co-reporter:Kai GUO, Qigao CAO, Jingtai ZHAO
Journal of Rare Earths 2013 Volume 31(Issue 11) pp:1029-1038
Publication Date(Web):November 2013
DOI:10.1016/S1002-0721(12)60398-6
Zintl phase compounds AM2Sb2 (A=Ca, Sr, Ba, Eu, Yb; M=Zn, Cd) is a new class of promising thermoelectrics owing to their intrinsic features in electronic and crystal structure, such as a small or even disappeared band-gap, large density-of-states at the Fermi level, covalently bonded network of M-Sb, as well as the layered stacking by cations A2+ and anionic slabs (M2Sb2)2−. In addition, the rich solid-state chemistry of Zintl phase allows structural modification and chemical substitution to adjust the fundamental transport parameters (carrier concentration, mobility, effective mass, electronic and lattice thermal conductivity) for improving the thermoelectric performance. In the present review, the recent advances in synthesis and thermoelectric characterization of title compounds AM2Sb2 were presented, and the effects of alloying or substitution for sites A, M and Sb on the electrical and thermal transport were emphasized. The structural disorder yielded by the incorporation of multiple ions significantly increased the thermoelectric figure of merit mainly resulted from the reduction of thermal conductivity without disrupting the carrier transport region in substance. Therefore, alloying or substitution has been a feasible and common route utilized to enhance thermoelectric properties in these Zintl phase compounds, especially for YbZn0.4Cd1.6Sb2 (ZT700 K=1.26), EuZn1.8Cd0.2Sb2 (ZT650 K=1.06), and YbCd1.85Mn0.15Sb2 (ZT650 K=1.14).Zintl phase compounds AM2Sb2 (A=Ca, Sr, Ba, Eu, Yb; M=Zn, Cd) show inspiring TE efficiency since they have intrinsic features in electronic and crystal structure desired for TE materials development, such as a small or even disappeared band-gap, large density-of-states at the Fermi level, covalently bonded network of M-Sb, as well as the layered stacking by cations and anionic slabs
Co-reporter:Biqiu LIU, Lisha LIU, Kai GUO, Jiao WANG, Linlin ZHU, Hui ZHANG, Wen WEN, Tieying YANG, Jingtai ZHAO
Journal of Rare Earths 2013 Volume 31(Issue 8) pp:745-749
Publication Date(Web):August 2013
DOI:10.1016/S1002-0721(12)60352-4
Co-reporter:Chen-Yang Wang, Guan-Qin Hu, Zhi-Jun Zhang, Bi-Qiu Liu, Lin-Lin Zhu, Hong Wang, Hao-Hong Chen, Ke Yang, Jing-Tai Zhao
Journal of Non-Crystalline Solids 2013 Volume 363() pp:84-88
Publication Date(Web):1 March 2013
DOI:10.1016/j.jnoncrysol.2012.12.014
Bi2O3–SiO2–Al2O3 based glasses of good transparency with high Bi2O3 content (~ 36 mol%) have been obtained by using melting method. Glass transition, crystallization and phase reaction temperatures of as-synthesized glass have been characterized by differential scanning calorimetry (DSC). The X-ray diffraction (XRD) analysis confirms the amorphous structure of the glass samples before and after the annealing. Ultraviolet and visible transmittance spectra show that the transmittance of as-synthesized glasses (0.6 mm thickness) can reach up to 80.1% in the visible region (above 550 nm), with the cutoff wavelength at 386 nm. The linear absorption coefficient (α), optical mobility gap (Eopt) as well as Urbach energy (ΔE) are calculated from optical transmittance. After annealing at 550 °C, the transmittance increases slightly near the absorption edge which shifts itself towards shorter wavelength. The roles of composition, heating and annealing profile on the transmittance of glasses have been discussed. For Bi2O3–SiO2–Al2O3 glasses with high Bi2O3 content, the Hruby factor is about 0.26, suggesting good stability.Highlights► Bi2O3–SiO2–Al2O3 glasses with high Bi2O3 content were prepared for the first time. ► The glasses obtained are of high transparency, about 80% (0.6 mm thickness). ► The content of Al2O3 has a great influence on the transmittance of glasses. ► The annealing can alter the transmittance and absorption edge. ► The Hruby factor of glass is about 0.26, indicating the good stability.
Co-reporter:Bi-Qiu Liu, Kai Guo, Jiao Wang, Zhi-Jun Zhang, Ye Tao, Yan Huang, Jing-Tai Zhao
Materials Letters 2013 100() pp: 245-247
Publication Date(Web):
DOI:10.1016/j.matlet.2013.03.024
Co-reporter:Xuemei Zhang, Jiao Wang, Kai Guo, Haohong Chen, Xinxin Yang, Jingtai Zhao
Journal of Alloys and Compounds 2012 Volume 517() pp:149-156
Publication Date(Web):15 March 2012
DOI:10.1016/j.jallcom.2011.12.068
Europium-doped yttrium hydroxide (Y(OH)3:Eu) with flower-like microstructure has been successfully prepared via a facile hydrothermal process, using potassium sodium tartrate (C4H4O6KNa) as a structure-directing reagent. Europium-doped yttrium oxide (Y2O3:Eu) with similar morphology is prepared by calcining the as-prepared Y(OH)3:Eu at 700 °C for 4 h. Influencing factors such as the concentration of potassium sodium tartrate, the amount of sodium hydroxide, and the temperature used for hydrothermal synthesis are systematically investigated. Possible formation mechanism for the flower-like microstructure is proposed on the basis of time-dependent experiment. Y2O3:Eu samples show a strong red emission corresponding to the 5D0-7F2 transition of Eu3+ ions under excitation. Emission intensity varies between samples with different morphologies. The optimum Eu3+ doping concentration is also explored. This work sheds some light on the design and preparation of novel microstructures.Highlights► We report a simple tartrate-assisted hydrothermal route to synthesis a novel flower-like Y(OH)3:Eu microstructure. ► The morphology was preserved after heat treatment to obtain flower-like Y2O3:Eu. ► A possible formation mechanism was proposed based on time-dependent experiments. ► Luminescence properties of products were investigated in detail.
Co-reporter:Hong Wang, Hao-Hong Chen, Horst Borrmann, Zhi-Jun Zhang, Jing-Tai Zhao
Journal of Alloys and Compounds 2012 Volume 545() pp:135-138
Publication Date(Web):25 December 2012
DOI:10.1016/j.jallcom.2012.08.049
In this work, a new type of lead tungstate crystal (Pb3WO6) was synthesized by hydrothermal method under high temperature and high pressure. Crystal structure was characterized by single-crystal X-ray structure determination. Pb3WO6 (monoclinic, P21/c, (No. 14), a = 7.8643(6) Å, b = 9.2036(8) Å, c = 9.0652(8) Å, β = 90.299(5)°, V = 656.13(2) Å3, Z = 4) exhibited two different layered arrangements of edge-shared octahedral WO6 with six oxygen coordination along a axis. Thermal stability was investigated by TG–DSC and two phase transformations were observed at about 647 and 748 °C, respectively. Finally, VUV excitation and emission spectra of Pb3WO6 crystal were studied under the temperature 14 K. The results revealed that samples had weak luminescent properties, which exhibited excitation peak at 285 nm and emission peak at 460 nm at low temperature.Highlights► A new type lead tungstate crystal Pb3WO6 was grown by hydrothermal technique under high temperature and high pressure. ► The structure was determined by single-crystal X-ray diffraction. ► The thermal properties and scintillating properties were studied by TG–DSC and low-temperature VUV spectra, respectively. ► The relationship between structure and properties was discussed systematically.
Co-reporter:Jin-You Liu, Jiao Wang, Zhi-Jun Zhang, Hao-Hong Chen, Xin-Xin Yang, Ren-Fu Li, Jing-Tai Zhao
Journal of Luminescence 2012 Volume 132(Issue 11) pp:2874-2878
Publication Date(Web):November 2012
DOI:10.1016/j.jlumin.2012.05.029
Undoped and Eu3+ activated Ln3BWO9 (Ln=Y, La, Gd) were prepared by the Pechini method and characterized with X-ray diffraction (XRD) and ultraviolet (UV) spectroscopy. All the samples have the hexagonal phase after heat treatment in the range of 850–1000 °C. The Eu3+ doped samples emit high-purity red light with peak maximum at about 617 nm under excitation of UV light (∼285 nm) at room temperature. When the doping concentration of Eu3+ is about 20–30%, luminescence intensity reaches the maximum. Luminescence decay curves indicate that Ln3BWO9:Eu3+ exhibits a fast decay time of about 0.5 ms. A possible luminescence mechanism has also been proposed. It is worth noting that both the absorption of host lattice and the charge transfer (CT) transition of Eu3+ are of great importance to the promising luminescent performance of Ln3BWO9:Eu3+.Highlights► Undoped and Eu3+ doped Ln3BWO9 (Ln=Y, La, Gd) were synthesized by a soft chemical method. ► Low temperature and room temperature photoluminescent properties have been studied. ► The Ln3BWO9:Eu3+ (Ln=Y, La, Gd) samples emit red light with high color–purity, and fast decay time of about 0.5 ms. ► A possible luminescence mechanism has been proposed.
Co-reporter:Xue-Mei Zhang, Man-Lian Huang, Zhi-Jun Zhang, Bi-Qiu Liu, Jing-Tai Zhao
Materials Letters 2012 Volume 68() pp:269-272
Publication Date(Web):1 February 2012
DOI:10.1016/j.matlet.2011.10.062
An interesting daisy-like Y(OH)3:Eu microstructure was successfully prepared via a facile hydrothermal process employing potassium sodium tartrate (C4H4O6KNa) as a structure-directing agent for the first time. Y2O3:Eu with the same morphology was obtained by calcining Y(OH)3:Eu precursor at 800 °C for 5 h. Phase and morphology of the products were investigated by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM) respectively. It was found that the concentrations of NaOH and C4H4O6KNa played crucial roles in controlling particle size and morphology of precursor. A possible formation mechanism of the novel microstructure was proposed. The daisy-like Y2O3:Eu microstructure had a stronger photoluminescence (PL) intensity than the microrod and reference nanoparticle.Highlights► A simple hydrothermal method to prepare a novel daisy-like Y(OH)3:Eu microstructure. ► This microstructure preserved after heat treatment. ► NaOH and C4H4O6KNa play important roles for the formation of unique microstructure. ► Microscale Y2O3:Eu shows stronger emission intensity than the nanoscale counterpart.
Co-reporter:Kai Guo, Man-Lian Huang, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao
Journal of Non-Crystalline Solids 2012 Volume 358(Issue 1) pp:88-92
Publication Date(Web):1 January 2012
DOI:10.1016/j.jnoncrysol.2011.08.032
Amorphous and nano-crystalline Y3Al5O12:Tb phosphor samples were obtained via a facile combustion method by calcination at various temperatures, using yttrium oxide and aluminum nitrite as starting materials and citric acid as fuel. XRD, FT-IR and TEM results showed that the products were amorphous if prepared at 750 °C, well-crystalline when treated above 850 °C. In addition, partially crystalline YAG phase was observed at 800 °C (in air). The excitation spectra of the samples calcined at 750 °C and 800 °C exhibited some difference in the 230–255 nm range in comparison to those of nano-crystalline YAG:Tb, i.e. an extra band centered at 250 nm was detected via Gaussian curve-fitting. Furthermore, the photoluminescence intensity of as-synthesized samples decreased obviously with increasing the crystallinity under 250 nm excitation. Contrary, it increased monotonously when altering the excitation wavelength to 323 nm. The concentration-dependent emission spectra of samples calcined at 800 °C revealed that the strongest intensity could be obtained with 10% Tb doping. Red-shifts indicated changes of the inter-atomic distances within the Tb3+ coordination polyhedron with increasing Tb concentration. The low temperature photoluminescence of partially crystalline YAG:10% Tb was also investigated, displaying good-resolution but reduced intensity compared to the room-temperature photoluminescence.Highlights► Amorphous YAG:Tb phosphor samples can be obtained via a facile sol–gel combustion method. ► The photoluminescence intensity decreases under 250 nm excitation with increasing the crystallinity. ► The strongest intensity of samples annealed at 800 °C could be obtained with 10% Tb doping. ► Red-shifts derive from the deformation of inter-atomic distances within the Tb3+ coordination polyhedron. ► A matrix consisting of various amorphous YAG:Tb contents can be applied for an advanced anti-bogus label.
Co-reporter:Kai Guo, Zhen-Yong Man, Xiao-Jun Wang, Hao-Hong Chen, Mei-Bo Tang, Zhi-Jun Zhang, Yuri Grin and Jing-Tai Zhao
Dalton Transactions 2011 vol. 40(Issue 39) pp:10007-10013
Publication Date(Web):06 Sep 2011
DOI:10.1039/C1DT10721F
An efficient route to construct a three-dimensional crystal structure is stacking of two-dimensional building blocks (2D-BBs). The crystal structures of potential thermoelectric compounds REOZnSb (RE = La, Ce, Pr, Nd) were virtually constructed from insulating [REO] and conducting [ZnSb] layers. Further optimizations performed by means of first-principles calculations show that REOZnSb should exhibit semimetal or narrow band-gap semiconductor behaviors, which is a prerequisite for high thermoelectric efficiency. The analysis of the electron localizability indicator for LaOZnSb reveals mostly covalent polar interactions between all four kinds of atoms. The electron density yields completely balanced ionic-like electronic formula La1.7+O1.2−Zn0.4+Sb0.9−. Furthermore, the samples of REOZnSb have been synthesized via solid-state reaction, and their crystal structures were confirmed by powder X-ray diffraction. The differences in cell parameters between the theoretically optimized and the experimental values are smaller than 2%. The temperature dependence of the magnetic susceptibility shows that LaOZnSb is diamagnetic above 40 K, whereas CeOZnSb, PrOZnSb and NdOZnSb are Curie–Weiss-type paramagnets. Electrical conductivity and Seebeck effect measurements indicate that REOZnSb are p-type semiconductors. A considerably high Seebeck coefficient and low thermal conductivity were obtained for pure LaOZnSb, but its low electrical conductivity leads to a small ZT. The high adjustability of the crystal structure as well as properties by optimization of the chemical composition in the compounds REOZnSb provide good prospects for achieving high thermoelectric efficiency.
Co-reporter:Kai Guo;Qi-Gao Cao;Xian-Juan Feng;Mei-Bo Tang;Hao-Hong Chen;Xiangxin Guo;Ling Chen;Yuri Grin
European Journal of Inorganic Chemistry 2011 Volume 2011( Issue 26) pp:4043-4048
Publication Date(Web):
DOI:10.1002/ejic.201100282
Abstract
Samples of Zintl phase YbCd2–xMnxSb2 (CaAl2Si2-type, space group Pm1) were prepared by a solid-state reaction followed by a suitable annealing and spark plasma sintering (SPS) for densification. Investigations were carried out on chemical substitution of Cd by Mn in order to optimize the thermoelectric figure of merit ZT in the solid solution system YbCd2–xMnxSb2 (x = 0, 0.05, 0.1, 0.15, 0.2, 0.4, 0.6, 0.8, 1.0, 1.5 and 2.0). Seebeck coefficients, electrical and thermal conductivities of all the samples were measured in the temperature range 300–650 K. The presence of Mn (x ≤ 0.2) substantially reduces the thermal conductivity and enlarges the Seebeck coefficient, meanwhile decreasing the electrical conductivity to a certain degree. As the concentration of Mn (x) becomes higher than 1.0, the semimetallic nature ofYbCd2–xMnxSb2 changes to that of a semiconductor with the majority the carriers switching from holes to electrons. Of all the samples, polycrystalline YbCd1.85Mn0.15Sb2 (p-type charge carriers) shows the highest figure of merit ZT of 1.14 at 650 K.
Co-reporter:Jiao Wang, Zhi-Jun Zhang, Jing-Tai Zhao, Hao-Hong Chen, Xin-Xin Yang, Ye Tao and Yan Huang
Journal of Materials Chemistry A 2010 vol. 20(Issue 48) pp:10894-10900
Publication Date(Web):18 Oct 2010
DOI:10.1039/C0JM01814G
Three-dimensional (3D) Y2WO6 and Y2WO6: Ln3+ microspheres with novel controllable morphology have been obtained by the hierarchical self-assembly via a hydrothermal synthesis route with a subsequent heat treatment. The amount of citric acid and polyvinylpyrrolidone (PVP) play crucial roles in the controlling of the morphologies. Hollow, core/shell as well as waxberry-shape Y2WO6 microspheres can be prepared in different reaction systems under the same facile hydrothermal conditions. Metastable phases of the samples form when they are crystallized at low temperature, which transfer to the thermodynamically stable counterpart above 1100 °C. This phase transformation is irreversible. The mechanism of reaction and self-assembly evolution process are proposed. The as-prepared Y2WO6:Ln3+ (Ln = Eu, Er, Sm, and Dy) samples show strong multi-color visible light emission under ultraviolet-visible light excitation. Compared with the monoclinic one, this metastable Y2WO6: Eu3+ phase exhibits different luminescent properties. Due to multi-color luminescent properties, these Ln3+-doped (Ln = Eu, Er, Sm, and Dy) metastable Y2WO6 morophologies controllable microspherical samples may be promising for further fundamental research and find applications in color displays.
Co-reporter:Hui Zhang, Michael Baitinger, Mei-Bo Tang, Zhen-Yong Man, Hao-Hong Chen, Xin-Xin Yang, Yi Liu, Ling Chen, Yuri Grin and Jing-Tai Zhao
Dalton Transactions 2010 vol. 39(Issue 4) pp:1101-1104
Publication Date(Web):25 Sep 2009
DOI:10.1039/B916346H
The thermoelectric performance of EuZn2Sb2 and EuCd2Sb2 was optimized by mixed occupation of the transition metal position. Samples in the solid solution Eu(Zn1−xCdx)2Sb2 with the CaAl2Si2-type crystal structure (space group m1) were prepared from the elements for compositions with x = 0, 0.1, 0.3, 0.5 and 1. The thermoelectric properties were investigated after densification of the products by spark plasma sintering (SPS). The samples show low electrical resistivity, high thermopower and a low lattice thermoconductivity. The highest ZT value of 1.06 at 650 K is obtained for x = 0.1.
Co-reporter:Kai Guo, Hao-Hong Chen, Xiangxin Guo, Xin-Xin Yang, Fang-Fang Xu, Jing-Tai Zhao
Journal of Alloys and Compounds 2010 Volume 500(Issue 1) pp:34-38
Publication Date(Web):18 June 2010
DOI:10.1016/j.jallcom.2010.03.037
Highly sinterable yttrium aluminum garnet (YAG) nano-powders have been synthesized by a sol–gel combustion method with various chelating agents and fuels, namely citric acid, tartaric acid, glycine and ethylene diamine tetraacetic acid (EDTA). The preparation involved the thermal decomposition of a chelating agent (fuel)–nitrate gel and the formation of amorphous precursors. The as-synthesized precursors were studied by infrared spectroscopy (IR), thermogravimetric (TG) and differential scanning calorimetric (DSC) analyses. The nano-powders calcined at 1000 °C were characterized by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). It was found that the chelating agents and fuels used had a significant influence on the average grain size and agglomeration of YAG nano-powders. The rate of combustion reaction between chelating agent (fuel) and nitrate was responsible for the growth of the grains. Nano-particles with the smallest size and high sinterability were obtained when using EDTA, which derived from the significant blocking of the diffusion path associated with the lowest combustion reaction rate.
Co-reporter:Hui Zhang, Liang Fang, Mei-Bo Tang, Hao-Hong Chen, Xin-Xin Yang, Xiangxin Guo, Jing-Tai Zhao, Yuri Grin
Intermetallics 2010 Volume 18(Issue 1) pp:193-198
Publication Date(Web):January 2010
DOI:10.1016/j.intermet.2009.07.011
High density polycrystalline CaCd2Sb2 and EuCd2Sb2 intermetallics are synthesized by Spark Plasma Sintering and their thermoelectric properties are investigated. X-ray diffraction measurements reveal both materials have a structure in R3¯m space group, containing a small amount of CdSb as a second phase. Thermoelectric measurements indicate both are p-type conductive materials. The figure of merit value of CaCd2Sb2 is 0.04 at 600 K and that of EuCd2Sb2 is 0.60 at 617 K. Theoretical calculations show that CaCd2Sb2 is a degenerate semiconductor with a band gap of 0.63 eV, while EuCd2Sb2 is metallic with DOS of 13.02 electrons/eV. For deeper understanding of the better thermoelectric properties of EuCd2Sb2, its low temperature magnetic, transport and heat capacity properties are investigated. Its Nèel temperature is 7.22 K, convinced by heat capacity anomaly at 7.13 K. Hall effect convinced that it is a p-type conductive material. It has high Hall coefficient, high carrier concentration and high carrier mobility of +1.426 cm3/C, 4.38 × 1018/cm3 and 182.40 cm2/Vs, respectively. They are all in the magnitude of good thermoelectric materials. The Eu 4f level around Fermi energy and antiferromagnetic order may count for the better thermoelectric properties of EuCd2Sb2 than that of CaCd2Sb2.
Co-reporter:Kai Guo, Xue-Mei Zhang, Hao-Hong Chen, Xin-Xin Yang, Xiangxin Guo, Jing-Tai Zhao
Materials Research Bulletin 2010 45(9) pp: 1157-1161
Publication Date(Web):
DOI:10.1016/j.materresbull.2010.05.029
Co-reporter:Ding-Bang Xiong;Yu-Feng Zhao;Lubomir D. Gulay
European Journal of Inorganic Chemistry 2009 Volume 2009( Issue 29-30) pp:4522-4527
Publication Date(Web):
DOI:10.1002/ejic.200900425
Abstract
Lanthanum phosphite microspheres with diameters of 80–100 μm were obtained under hydrothermal conditions by using lanthanum oxalate as precursor. The surfaces of these spherules consist of well-orientated submicron-sized rods with typical diameters of 300 nm and lengths of 6 μm. The possible mechanism of formation of this morphology was suggested. The product is a new phase, and its crystal structure was determined by ab initio methods from high-resolution conventional X-ray powder diffraction analysis. Chains consisting of face-sharing LaO9 polyhedra were observed; these chains form three-dimensional compact frameworks by sharing vertexes in the ab plane and edges along the c axis. The sample doped with Ce3+ showed an intensive broad emission band with a maximum around 364 nm under UV excitation.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)
Co-reporter:Hui Zhang, Jing-Tai Zhao, Mei-Bo Tang, Zhen-Yong Man, Hao-Hong Chen, Xin-Xin Yang
Journal of Physics and Chemistry of Solids 2009 Volume 70(Issue 2) pp:312-315
Publication Date(Web):February 2009
DOI:10.1016/j.jpcs.2008.10.020
Structural, magnetic, heat capacity, electrical and thermal transport properties are reported on polycrystalline Ba8Ni6Ge40. Ba8Ni6Ge40 crystallizes in a cubic type I clathrate structure with unit cell a=10.5179 (4) Å. It is diamagnetic with susceptibility χdia=−1.71×10–6 emu/g Oe. An Einstein temperature 75 K and a Debye temperature 307 K are estimated from heat capacity data. It exhibits n-type conducting behavior below 300 K. It shows high Seebeck coefficients (−111×10–6 V/K), low thermal conductivity (2.25 W/K m), and low electrical resistivity (8.8 mΩ cm) at 300 K.
Co-reporter:Ding-Bang Xiong, Zhi-Jun Zhang, Lubomir D. Gulay, Mei-Bo Tang, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao
Inorganica Chimica Acta 2009 Volume 362(Issue 9) pp:3013-3018
Publication Date(Web):1 July 2009
DOI:10.1016/j.ica.2009.01.041
A new compound Gd4(H2O)5(HPO3)6 (1) was isolated from the reaction of gadolinium chloride GdCl3 · nH2O with H3PO3 under hydrothermal conditions. The crystal structure was solved by means of single-crystal X-ray diffraction. The structure is composed of parallel gadolinium–oxygen polyhedra chains connected by phosphite ions, and shows three-dimensional (3D) open-framework with eight-membered ring (8MR) channels. The structure is different from its counterpart Eu2(H2O)2.5(PO3H)3 due to the effect of lanthanide contraction. The intensive intrinsic UV emission of this compound at λmax = 312 nm comes from the spin-forbidden 6P7/2 → 8S7/2 f–f transition of the Gd3+ ions. No magnetic order was observed for this compound.A new compound Gd4(H2O)5(HPO3)6 was obtained by hydrothermal methods. The crystal structure is built up of parallel gadolinium–oxygen polyhedra chains connected into three-dimensional (3D) open-framework by phosphite ions, showing eight-membered ring channels. The compound shows intrinsic intensive UV emission around 312 nm and no magnetic order was observed.
Co-reporter:Zhi-Jun Zhang, Shuang Chen, Jiao Wang, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao, Ye Tao, Yan Huang
Optical Materials 2009 Volume 32(Issue 1) pp:99-103
Publication Date(Web):November 2009
DOI:10.1016/j.optmat.2009.06.012
The VUV excited luminescent properties of Ce3+, Eu3+ and Tb3+ in the matrices of KMLn(PO4)2 (M2+ = Ca, Sr; Ln3+ = Y, La, Lu) were investigated. The bands at about 155 nm in the VUV–UV excitation spectra are attributed to the host lattice absorption, which indicates that the optical band gap of KMLn(PO4)2 is about 8.0 eV. Ce3+-doped samples show typical Ce3+ emission in the range of 300–450 nm, and the energy transfer from host lattice to Ce3+ is efficient. For Eu3+-doped samples, the O2−–Eu3+ CTBs are observed to be at about 228 nm except KSrLu(PO4)2:Eu3+ (247 nm). As for Tb3+-doped samples, typical 4f → 5d absorption bands in the region of 175–250 nm were observed.
Co-reporter:Zhi-Jun Zhang, Jun-Lin Yuan, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao, Guo-Bin Zhang, Chao-Shu Shi
Solid State Sciences 2009 Volume 11(Issue 2) pp:549-555
Publication Date(Web):February 2009
DOI:10.1016/j.solidstatesciences.2008.07.008
The luminescent characteristics of RE (RE3+ = Eu, Tb, Dy, Sm and Tm)-doped K2GdZr(PO4)3 have been investigated. The band in the range of 130–157 nm in the VUV excitation spectra of these compounds is attributed to the host lattice or PO43− group absorption and the band from 157 nm to 215 nm with the maximum at 188 nm is due to the O–Zr charge transfer transition. For Eu3+-doped sample, the relatively weak band of O2−–Eu3+ charge transfer (CTB) at 222 nm is observed and for Tb3+-doped sample, the band at 223 nm is related to the 4f–5d spin-allowed transition of Tb3+. For Dy3+- and Sm3+-doped samples, the O2−–Dy3+ and O2−–Sm3+ CTBs have not been observed, probably due to the 2p electrons of oxygen tightly bound to the zirconium ion in the host lattice. In Tm3+-doped sample, the weak O2−–Tm3+ CTB is located at 170 nm. It is observed that there is energy transfer between the host and the luminescent activators (e.g. Eu3+, Tb3+ and Sm3+) except for Tm3+.The crystal structure of the cubic phase K2GdZr(PO4)3 consists of [(GdZr)P3O18] units, each PO43− group forms a tetrahedron and each of the Gd/Zr atoms is surrounded by six oxygen atoms to form a small distorted octahedron. The cavities in the [(GdZr)P3O18] framework contain potassium atoms with an irregular coordination.
Co-reporter:Shuang Chen;Ming Ye;Hao-Hong Chen
Journal of Inorganic and Organometallic Polymers and Materials 2009 Volume 19( Issue 2) pp:139-142
Publication Date(Web):2009 June
DOI:10.1007/s10904-008-9245-5
Boron phosphate (BPO4) is a well known catalyst for a range of organic chemical reactions. In this paper, we report the preparations and characterizations of nano-sized BPO4 and nano-BPO4-based core-shell spheres. The samples were synthesized hydrothermally using H3BO3, H3PO4 and short chain n-alkylamines (n = 3, 4) as starting materials. The resulting products were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scan electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. A possible mechanism for the formation of the materials is also discussed.
Co-reporter:Xiao-Jun Wang, Ming-Hui Ge, Zhen-Yong Man, Jing-Tai Zhao
Journal of Alloys and Compounds 2008 Volume 453(1–2) pp:316-319
Publication Date(Web):3 April 2008
DOI:10.1016/j.jallcom.2006.11.143
n-Alkylammonium dihydrogen phosphates are the compounds comprised of organic alkyl ammonia cation and dihydrogen phosphate anion. These compounds can absorb ultraviolet and emit white visible light predominated by blue emission. Even afterglow as long as 4 min will be observed when they are exposed to 254 nm ultraviolet radiation. For the compounds without π orbits no metal ions luminescence center, it is difficult to explain these luminescence phenomena through normal theory. Therefore, the first principle studies were introduced to explore the electronic structures of these compounds. The calculational results demonstrate that the orbits energy levels of these compounds do not depend on the number of carbon atoms and ultraviolet absorption is supposed to be not derived from intrinsic orbits but some extrinsic levels. Combining with the optical spectrums, it is quite likely that the novel optical properties are linked with the hydrogen defects from dihydrogen phosphate anions. Furthermore, our results suggest that the generalized gradient approximation (GGA) methods are more appropriate than local density approximation (LDA) to calculate these compounds own hydrogen bonds.
Co-reporter:Zhijun Zhang, Hui Zhang, Chengjun Duan, Junlin Yuan, Xiaojun Wang, Dingbang Xiong, Haohong Chen, Jingtai Zhao
Journal of Alloys and Compounds 2008 Volume 466(1–2) pp:258-263
Publication Date(Web):20 October 2008
DOI:10.1016/j.jallcom.2007.11.050
The crystal structure of Lu2WO6 was determined from Rietveld refinement of X-ray powder diffraction data. It crystallizes in the monoclinic system belonging to space group P2/c (No.13) with lattice parameters: a = 7.5180(1) Å, b = 5.2675(1) Å, c = 11.2245(2) Å, β = 104.61(0)°, V = 430.14(11) Å3, Z = 4. The conventional R indices obtained are Rp = 0.090, Rwp = 0.119 and RB = 0.075. The infinite chain comprised of Lu(2)O8 dodecahedra and Lu(3)O7 decahedra makes up the layer A, and the infinite straight chain is built of four-ring of polyhedra in which the WO6 and Lu(1)O8 groups alternate in layer B, finally, this structure is formed by stacking of these two layers with edge-shared. The X-ray and UV excited luminescence properties of Eu3+ and Pr3+ in Lu2WO6 were investigated: Eu3+ shows high luminescent efficiency in emitting red light, and Pr3+ is less efficient in emitting orange light. The luminescent mechanism of Eu3+ and Pr3+ in the matrix of Lu2WO6 is much different.
Co-reporter:Cheng-Jun Duan, Wei-Feng Li, Jun-Lin Yuan, Jing-Tai Zhao
Journal of Alloys and Compounds 2008 Volume 458(1–2) pp:536-541
Publication Date(Web):30 June 2008
DOI:10.1016/j.jallcom.2007.04.127
A new compound LuBa3B9O18 has been prepared by a high-temperature solid-state reaction and its crystal structure was determined by powder X-ray diffraction methods. The results of Rietveld refinement show that it is isotypic to YBa3B9O18. The X-ray excited luminescent properties of LuBa3B9O18 were investigated. It shows a broad emission band in the wavelength range of 300–550 nm with peak center at 385 nm. Its room temperature fluorescent decay profile exhibits a single-exponent shape with decay time of 15 ns. It is believed that the lattice defects have played an important role on the luminescent performances of LuBa3B9O18 powders and its thermal luminescence measurement confirmed the existence of lattice defects in it. Considering the emission wavelength, luminescence intensity, decay time, melting point, density and non-hygroscopic property of LuBa3B9O18, one has reason to assume that it might find an application as a new scintillation material.
Co-reporter:Jun-Lin Yuan, Jiao Wang, Zhi-Jun Zhang, Jing-Tai Zhao, Guo-Bin Zhang
Optical Materials 2008 Volume 30(Issue 8) pp:1327-1334
Publication Date(Web):April 2008
DOI:10.1016/j.optmat.2007.06.017
AGdP2O7 (A = Rb, Cs) diphosphates were obtained through solid state reactions. Besides the monoclinic β-RbGdP2O7 and CsGdP2O7, the high temperature phase of RbGdP2O7, α-RbGdP2O7, was reported for the first time, which is isostructural with α-KYP2O7 (S.G. Cmcm, Z = 4), and the unit cell volume of α-phase is 5.4% smaller than that of β-phase. However, no reverse α ↔ β polymorphic transition was observed. The VUV-UV and X-ray excited spectroscopic properties of undoped and Ln3+ (Ln = Ce, Eu, Tb) doped AGdP2O7 (A = Rb, Cs) were presented. Under X-ray excitation, strong cascade emission of Gd3+ was observed in each undoped AGdP2O7 samples. The Gd–Ln energy transfer is relatively weak, which is due to the large Gd–Gd distance. The energy transfer probability among Gd3+ ions follows a sequence of CsGdP2O7 < β-RbGdP2O7 < α-RbGdP2O7, which is inversely proportional with the Gd–Gd distance.
Co-reporter:Jun-Lin Yuan, Hui Zhang, Jing-Tai Zhao, Hao-Hong Chen, Xin-Xin Yang, Guo-Bin Zhang
Optical Materials 2008 Volume 30(Issue 9) pp:1369-1374
Publication Date(Web):May 2008
DOI:10.1016/j.optmat.2007.07.004
A new structural type of rare earth metaphosphate, Lu(PO3)3, was prepared from high-temperature solution, of which the crystal structure was solved in S.G. of Cc (No.9) and Z = 4 with unit cell dimensions of a = 13.972(3) Å, b = 6.6710(13) Å, c = 9.958(2) Å and β = 127.36(3)°. In Lu(PO3)3, [LuO6] octahedra connect with the non-bridging oxygens on (PO3)n infinite zigzag chains that extended along c-axis. The VUV and X-ray excited luminescent properties of undoped and Ln3+ (Ln = Ce, Eu, Tb) doped samples were examined, from which the optical band gap was estimated to be 8.3 eV. Besides, in the undoped sample a STE emission within 320–480 nm was observed, which probably be related to oxygen defects. However, in the Lu(PO3)3:Ce sample the Ce3+ emission was weak and STE emission was totally quenched under hard X-ray excitation.
Co-reporter:Shuang Chen, Horst Borrmann, Ya-Xi Huang, Zhi-Jun Zhang, Hao-Hong Chen and Jing-Tai Zhao
Langmuir 2008 Volume 24(Issue 17) pp:9323-9327
Publication Date(Web):July 22, 2008
DOI:10.1021/la801403s
A family of lamellar mesostructured n-alkylamine borophosphates, denoted CnA-BPO (BPO stands for inorganic borophosphate layer; n = 9−15, the number of carbon atoms in the n-alkylamine chain) has been prepared hydrothermally at 160 °C by using neutral n-alkylamines as templates. Those CnA-BPO compounds were characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric measurements, and differential thermal analysis (TG-DTA) as well as chemical analyses. Interestingly, these compounds may form a bilayer, a monolayer, or mixed state of bilayer and monolayer structures depending on the content of n-alkylamine. Linear relationships for both bilayer and monolayer compounds were observed between the interlayer distances and the numbers of carbon atoms in the n-alkylamine chain. The thickness of the inorganic layers, the arrangement of n-alkylamine in the interlayer space, and the composition of the compounds are proposed.
Co-reporter:Jun Lin Yuan, Jiao Wang, Ding Bang Xiong, Jing Tai Zhao, Yi Bing Fu, Guo Bin Zhang, Chao Shu Shi
Journal of Luminescence 2007 Volume 126(Issue 2) pp:717-722
Publication Date(Web):October 2007
DOI:10.1016/j.jlumin.2006.11.001
NaLaP2O7 and NaGdP2O7 powder samples are prepared by solid-state reactions at 750 and 600 °C, respectively, and the VUV-excited luminescence properties of Ln3+ (Ln=Ce, Pr, Tb, Tm, Eu) in both diphosphates are studied. Ln3+ ions in both hosts show analogous luminescence. For Ce3+-doped samples, the five Ce3+ 5d levels can be clearly identified. As for Pr3+ and Tb3+-doped samples, strong 4f–5d absorption band around 172 nm is observed, which matches well with Xe–He excimer in plasma display panel (PDP) devices. As a result, Pr3+ can be utilized as sensitizer to absorb 172 nm VUV photon and transfer energy to appropriate activators, and Tb3+-doped NaREP2O7(RE=La, Gd) are potential 172 nm excited green PDP phosphors. For Tm3+ and Eu3+-doped samples, the Tm3+–O2− charge transfer band (CTB) is observed to be at 177 nm, but the CTB of Eu3+ is observed at abnormally low energy position, which might originate from multi-position of Eu3+ ions. The similarity in luminescence properties of Ln3+ in both hosts indicates certain structural resemblance of coordination environment of Ln3+ in the two sodium rare earth diphosphates.
Co-reporter:Jun Lin Yuan, Xiao Jun Wang, Ding Bang Xiong, Cheng Jun Duan, Jing Tai Zhao, Yi Bing Fu, Guo Bin Zhang, Chao Shu Shi
Journal of Luminescence 2007 Volume 126(Issue 1) pp:130-134
Publication Date(Web):September 2007
DOI:10.1016/j.jlumin.2006.06.002
Spectroscopic properties of Ce3+ and Pr3+-doped AREP2O7-type alkali rare earth diphosphates (A=Na, K, Rb, Cs; RE=Y, Lu) have been investigated using VUV spectroscopy technique. Ce3+-doped samples show typical Ce3+ emission in the range of 325–450 nm. The strong host absorption band starting at around 160 nm indicates that the optical band gap of AREP2O7 hosts is at least 7.7 eV, and the host→Ce3+ energy transfer process is rather efficient. However, AREP2O7:Pr3+ samples show less efficient host→Pr3+ energy transfer. The direct Pr3+ 4f2→4f15d1 excitation, which are 12160±640 cm−1 higher respect to that of Ce3+, leads to strong 4f15d1→4f2 emission bands in the range of 230–325 nm but no obvious 4f2→4f2 emission lines.
Co-reporter:Ding-Bang Xiong, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao
Journal of Solid State Chemistry 2007 Volume 180(Issue 1) pp:233-239
Publication Date(Web):January 2007
DOI:10.1016/j.jssc.2006.09.034
Two new anhydrous sodium borophosphates with one-dimensional structure, Na3B6PO13(1) and Na3BP2O8(2), were synthesized by low-temperature molten salts techniques using boric acid and sodium dihydrogen phosphate as flux, respectively. The crystal structures were solved by means of single-crystal X-ray diffraction (1, orthorhombic, Pnma (no. 62), a=9.3727(4)Å, b=16.2307(7)Å, c=6.7232(3)Å, Z=4Z=4; 2 , monoclinic, C2/c (no. 15), a=12.567(4)Å, b=10.290(3)Å, c=10.210(3)Å, β=92.492(5)°β=92.492(5)°, Z=8Z=8). Compound 1 is characterized by an infinite chain of ∞1{[B6PO13]}3- containing eight-membered rings in which all vertexes of borate groups contribute to interconnection. Compound 2 reveals an infinite straight chain ∞1{[BP2O8]}3- built of vertex-sharing four-membered rings, and chains in neighboring layers arranged along different orientations. The relations between structures and the synthetic conditions with only traced water are discussed.Two new anhydrous sodium borophosphates Na3B6PO13 and Na3BP2O8 were synthesized by low-temperature molten salts techniques using boric acid and sodium dihydrogen phosphate as flux, respectively. Na3B6PO13 crystallize in Pnma and comprise infinite chain of ∞1{[B6PO13]}3-, and Na3BP2O8 crystallize in C2/c and comprise infinite chain of ∞1{[BP2O8]}3-.
Co-reporter:Jun-Lin Yuan, Xiao-Yan Zeng, Jing-Tai Zhao, Zhi-Jun Zhang, Hao-Hong Chen, Guo-Bin Zhang
Journal of Solid State Chemistry 2007 Volume 180(Issue 11) pp:3310-3316
Publication Date(Web):November 2007
DOI:10.1016/j.jssc.2007.09.023
A new efficient blue phosphor, Eu2+ activated SrZnP2O7, has been synthesized at 1000 °C under reduced atmosphere and the crystal structure and photoluminescence properties have been investigated. The crystal structure of SrZnP2O7 was obtained via Rietveld refinement of powder X-ray diffraction (XRD) pattern. It was found that SrZnP2O7 crystallizes in space group of P21/n (no. 14), Z=4, and the unit cell dimensions are: a=5.30906(2) Å, b=8.21392(3) Å, c=12.73595(5) Å, β=90.1573(3)°, and V=555.390(3) Å3. Under ultraviolet excitation (200–400 nm), efficient Eu2+ emission peaked at 420 nm was observed, of which the luminescent efficiency at the optimal concentration of Eu2+ (4 mol%) was estimated to be 96% as that of BaMgAl10O17:Eu2+. Hence, the SrZnP2O7:Eu2+ exhibit great potential as a phosphor in different applications, such as ultraviolet light emitting diode and photo-therapy lamps.The perspective view of SrZnP2O7 unit cell, which was obtained from Rietveld refinement. Eu2+ activated SrZnP2O7 is a new violet–blue emitting phosphor that has efficiency as high as 96% as that of BAM:Eu2+.
Co-reporter:Ding-Bang Xiong, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao
Inorganica Chimica Acta 2007 Volume 360(Issue 5) pp:1616-1620
Publication Date(Web):1 April 2007
DOI:10.1016/j.ica.2006.08.044
A new lanthanum ethylenediaminetetraacetate (EDTA) coordination polymer, {[La(EDTA)(H2O)]2}n (EDTA3− = [(CH2N)2(CH2COOH)(CH2COO−)3]), was hydrothermally prepared from LaCl3 solution and ethylenediaminetetracetic acid at 448 K. The compound was characterized by elemental analysis, FTIR, TG-DTA, and X-ray crystallography. The structure consists of ladder-like chains of [La(EDTA)(H2O)]2 dimers bridged by O–C–O groups. Hydrothermal method successfully reduced the high number of La-aqua coordinations in known lanthanum EDTA to one giving rise to relatively compact structure. It has high thermal stability up to 550 K. Every EDTA ligand with COOH group is involved in eight La–O(N) bonds to three nine-coordinated La centers.A new one-dimensional polymeric lanthanum EDTA, {[La(EDTA)(H2O)]2}n, was hydrothermally prepared. The structure consists of ladder-like chains of [La(EDTA)(H2O)]2 dimers bridged by O–C–O groups. Hydrothermal method successfully reduced the high number of metal-aqua coordination to one giving rise to relatively compact structure.
Co-reporter:Wei Liu, Ding-Bang Xiong, Xin-Xin Yang, Jing-Tai Zhao
Journal of Solid State Chemistry 2007 Volume 180(Issue 7) pp:2116-2120
Publication Date(Web):July 2007
DOI:10.1016/j.jssc.2007.04.031
A new chromium-phosphate has been prepared under hydrothermal conditions for the first time. It crystallizes in the Monoclinic system, space group C2/c, a=17.002(3) Å, b=26.333(5) Å, c=16.017(4) Å, β=96.63 (3)°, V=7123.07(2) Å3 and Z=4. The crystal structure displays a centrosymmetric complex aggregate [Cr9P12O58H12]17−, constructed from the unprecedented enneanucleus chromic core Cr9O10 with peripheral ligations provided by 12 phosphate groups. The sodium ions and water as guests fill in the cavities among the clusters to satisfy the charge balance and keep the structural stability. The magnetic measurement indicates the existence of antiferromagnetic interactions.Polyhedral representation of the oxo-chromium core in compound 1, showing the bridging function of phosphate groups around the octahedral chromium core (CrO6 octahedron, grey and transparent; Cr, green sphere; P, pink sphere; O, red sphere; H, small black sphere).
Co-reporter:Jun-Lin Yuan, Zhi-Jun Zhang, Xiao-Jun Wang, Hao-Hong Chen, Jing-Tai Zhao, Guo-Bin Zhang, Chao-Shu Shi
Journal of Solid State Chemistry 2007 Volume 180(Issue 4) pp:1365-1371
Publication Date(Web):April 2007
DOI:10.1016/j.jssc.2007.01.033
Three rare earth borosilicate oxyapatites, RE5Si2BO13 (RE=La, Gd, Y), were synthesized via wet chemical method, of which RE5Si2BO13 (RE=Gd, Y) were first reported in this work. In the three oxyapatites, [BO4] and [SiO4] share the [TO4] tetrahedral oxyanion site, and RE3+ ions occupy all metal sites. The differential scanning calorimetry–thermo gravimetry measurements and high temperature powder X-ray diffraction pattern revealed a vitrification process within 300–1200 °C, which was due to the glass-forming nature of borosilicates. From the VUV excitation spectra of Eu3+ and Tb3+ in RE5Si2BO13, the optical band gaps were found to be 6.31, 6.54 and 6.72 eV for RE5Si2BO13 (RE=La, Gd, Y), respectively. The emission and excitation bands of Eu3+ and Tb3+ are discussed relating with their coordination environments. Among the three hosts, Y5Si2BO13 would be the best for Eu3+ and Tb3+-doped phosphors.The perspective view of RE5Si2BO13 (RE=La, Gd, Y) oxyapatite along [001] direction. All non-tetrahedral metal sites are occupied by RE3+, and the tetrahedral sites by SiO4 and BO4 groups. Y5Si2BO13 is a good host for both Eu3+ and Tb3+ activated phosphors.
Co-reporter:Zhi-Jun Zhang, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao
Materials Science and Engineering: B 2007 Volume 145(1–3) pp:34-40
Publication Date(Web):20 December 2007
DOI:10.1016/j.mseb.2007.09.091
The samples of CaMoO4:Eu3+,Tb3+ have been synthesized via the Pechini method, and their luminescent properties were investigated. Both under UV and X-ray excitation, Eu3+ and Tb3+ ions show high luminescent efficiency in emitting red and green light in single doped samples, and the energy transfer from MoO4 tetrahedron unit to Eu3+ and Tb3+ ions occurred. When co-doped the Eu3+ and Tb3+ ions into the CaMoO4 matrix, it modified the luminescence spectra. At low concentration (≤1.5%), there is only the energy transfer transition from MoO4 unit to the activators. While at high concentration (>1.5%), there is not only the energy transfer from the host to the activators, but also the interaction between these activators: Tb3+ ion serves as the donor and Eu3+ ion serves as the acceptor. The energy transfer from Tb3+ to Eu3+ was studied via time-resolved fluorescence spectrum. By controlling the doping concentration, the luminescent color could be modified within the whole visible spectrum. From the standpoints of modified color and luminescent efficiency, they are attractive candidates in the manufacture of fluorescent lamps for advertising signs or other color raster displays.
Co-reporter:Ding-Bang Xiong Dr. Dr.;Hao-Hong Chen Dr.;Xin-Xin Yang
Chemistry - A European Journal 2007 Volume 13(Issue 35) pp:
Publication Date(Web):15 OCT 2007
DOI:10.1002/chem.200701009
A layered borogermanate with three-dimensional microporosity within the layers, K4[B8Ge2O17(OH)2] (monoclinic, space group: C2/c; a=12.095(2), b=6.7979(14), c=19.944(4) Å; β=93.04(3)°; V=1637.6(6) Å3; Z=4), has been synthesized in a flux of potassium borate. Because of its three-dimensional pore structure and thermal stability, the compound has the potential to eventually form nanocomposites with polymers and to be processed into thin microporous films.
Co-reporter:Ding-Bang Xiong, Man-Rong Li, Wei Liu, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao
Journal of Solid State Chemistry 2006 Volume 179(Issue 8) pp:2571-2577
Publication Date(Web):August 2006
DOI:10.1016/j.jssc.2006.04.035
Two new lanthanum phosphite hydrates, La2(H2O)(HPO3)3 (1) and La2(H2O)2(HPO3)3 (2), were synthesized by a hydrothermal method. Their crystal structures were determined by X-ray single-crystal method (1, monoclinic, C2/cC2/c (No. 15); a=20.820(5)Å, b=6.717(2)Å, c=14.123(3)Å, β=101.261(3)°β=101.261(3)°, V=1937.0(8)Å3; Z=8Z=8; 2, triclinic, P -1 (No. 2); a=8.168(3)Åa=8.168(3)Å, b=8.439(2)Å, c=9.337(3)Åc=9.337(3)Å, α=115.641(3)°α=115.641(3)°, β=98.655(3)°β=98.655(3)°, γ=105.124(3)°γ=105.124(3)°, V=533.87(1)Å3, Z=2Z=2). Both crystal structures present three-dimensional open-framework structures containing channels, and 1 adopts intersecting type. In the two structures, the face-sharing dimers of LaOn (n=8,9n=8,9) were observed. Other characterizations by IR and TG–DSC were also described. Furthermore, both the compounds doped with Ce+3 showed intensive broad emission band around 340 nm under UV excitation.Two lanthanum phosphites, La2(H2O)(HPO3)3 (1) and La2(H2O)2(HPO3)3 (2), were synthesized by modified hydrothermal methods and their crystal structures showed different arrangements of face-sharing dimers of La coordination polyhedron observed for the first time in rare-earth phosphites. The two Ce+3-doped compounds show intensive broad emission band around 340 nm under UV excitation.
Co-reporter:Man-Rong Li;Wei Liu;Hao-Hong Chen;Xin-Xin Yang;Zan-Bin Wei;Dun-Hua Cao;Mu Gu
European Journal of Inorganic Chemistry 2005 Volume 2005(Issue 23) pp:
Publication Date(Web):25 OCT 2005
DOI:10.1002/ejic.200500477
The first lutetium diphosphate NH4LuP2O7 has been prepared by a two-step, low-temperature self-flux synthesis in the presence of the F– anion, functioning as a mineralizer, which played a significant role in the synthetic process. The crystal structure has been characterized by single-crystal X-ray diffraction. The title compound crystallizes in a monoclinic system of the space group P21/c (No. 14), a = 7.651(2) Å, b = 10.789(2) Å, c = 8.577(2) Å, β = 105.75(3)°, V = 681.4(2) Å3, Z = 4. The three-dimensional framework of NH4LuP2O7, composed of Lu2P4O14 building units formed by vertex-linking LuO6 and P2O7 goups, is isostructural with compounds of the type KAlP2O7 in the ternary diphosphate(AIMIIIP2O7) system. X-ray-excited luminescence measurements of Ce-activated samples show insteresting scintillation properties with a short decay time of 16 ns at room temperature. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Co-reporter:Wei Liu;Hao-Hong Chen;Xin-Xin Yang
European Journal of Inorganic Chemistry 2005 Volume 2005(Issue 5) pp:
Publication Date(Web):15 MAR 2005
DOI:10.1002/ejic.200400644
Two transition-metal phosphites, Na2[M(HPO3)2] (M = Fe, Co) with a new structure type have been synthesised under mild hydrothermal conditions and the solid-state structures have been elucidated by single-crystal X-ray diffraction studies. The structures are of a new type with the following data: orthorhombic, Pnma, a = 12.169(4), b = 5.441(2) and c = 9.146(3) Å for the iron species 1 and a = 12.091(3), b = 5.400(4) and c = 9.115(2) Å for the cobalt compound 2, with Z = 4. The crystal structures of these compounds are isotypic and built up from a 3D open framework with 4-, 6- and 12-membered polyhedral rings of vertex-linked MO6 and HPO3 building units. The inorganic frameworks contains 12-membered ring channel systems in which the sodium ions are located. The topology of this structure type is remarkably similar to that of the aeschynite CaTa2O6 with much larger channels. Magnetic measurements of Na2[Co(HPO3)2] show different magnetic features in the low-temperature (5–30 K) and high-temperature ranges (100–320 K) suggesting the possible existence of a complex magnetic structure. Antiferromagnetic ordering can be observed as a broadened cusp in χ–1 at θ = 2.6 K. For Na2[Fe(HPO3)2], the magnetic behavior follows the Curie–Weiss law with μeff = 5.41 μB, fitted for 100–320 K. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005)
Co-reporter:Chengjun Duan, Junlin Yuan, Jingtai Zhao
Journal of Solid State Chemistry 2005 Volume 178(Issue 12) pp:3698-3702
Publication Date(Web):December 2005
DOI:10.1016/j.jssc.2005.09.026
The samples of YBa3B9O18, LuBa3(BO3)3, α-YBa3(BO3)3 and LuBO3 powders have been synthesized by the solid-state reaction methods at high temperature and their X-ray excited luminescent properties were investigated. All the studied materials show a broad emission band in the wavelength range of 300–550 nm with the peak centers at about 385 nm for YBa3B9O18 and LuBa3(BO3)3, 415 nm for α-YBa3(BO3)3 and 360 nm for LuBO3 powders, respectively. Even though those compounds have the different atomic structures, they have the common structural feature of each yttrium or lutetium ion bonded to six separate BO3 groups, i.e., octahedral RE(BO3)6 (RE=Lu or Y) moiety. This octahedral RE(BO3)6(RE=Lu or Y) moiety seems to be an important structural element for efficient X-ray excited luminescence of those compounds, as are the edge-sharing octahedral TaO6 chains for tantalate emission.Even though these compounds, YBa3B9O18, LuBa3(BO3)3, α-YBa3(BO3)3 and LuBO3, have the different atomic structures, they have the common structural feature of each yttrium or lutetium ion bonded to six separate BO3 groups, i.e., octahedral RE(BO3)6 (RE=Lu or Y) moiety. This octahedral RE(BO3)6(RE=Lu or Y) moiety seems to be an important structural element for efficient X-ray excited luminescence of those compounds, as are the edge-sharing octahedral TaO6 chains for tantalate emission.
Co-reporter:Wei Liu, Man-Rong Li, Xin-Xin Yang, Hao-Hong Chen, Jing-Tai Zhao
Journal of Solid State Chemistry 2005 Volume 178(Issue 3) pp:912-916
Publication Date(Web):March 2005
DOI:10.1016/j.jssc.2004.11.035
A novel one-dimensional copper (II) chlorophosphate, Na3[CuO(HPO4)Cl] has been prepared by using the low-temperature flux method. It crystallizes in the orthorhombic system, space group Pnma , a=11.096(2)a=11.096(2), b=6.5703(13)b=6.5703(13) and c=8.3623(17)Å, V=609.7(2)Å3, Z=4Z=4. Its crystal structure presents a one-dimensional character in such a way that the edge-sharing CuO4Cl2 building blocks yield a novel linear octahedral chains via Cu–O–Cu and Cu–Cl–Cu bridges. The HPO4 groups, as the modifier, are grafted onto these chains and sodium ions are located between the chains to satisfy the charge balance. The magnetic susceptibility obeys a Curie–Weiss law above 120 K with C=0.38C=0.38 (emu K)/mol and Θ=-150K, showing the Cu2+ character and antiferromagnetic interactions.
Co-reporter:Cheng-Jun Duan, Wei-Feng Li, Xue-Yan Wu, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao, Yi-Bing Fu, Ze-Ming Qi, Guo-Bin Zhang, Zhao-Shu Shi
Materials Science and Engineering: B 2005 Volume 121(Issue 3) pp:272-277
Publication Date(Web):15 August 2005
DOI:10.1016/j.mseb.2005.04.013
Novel phosphors of Ce3+, Tb3+, Sm3+ or Gd3+ doped Ba3BP3O12 were synthesized by the solid-state reaction method and their VUV–UV spectroscopic properties were investigated. The bands at about 165 nm in the VUV excitation spectra are attributed to the host lattice absorptions. The bands at about 216, 238, 269, 282, and 294 nm for the sample of Ba3BP3O12: Ce3+ are connected with the f–d transitions of the Ce3+ ion, the strong band at 220 nm and weak band at 260 nm for the sample of Ba3BP3O12: Tb3+ are assumed to be the lowest spin-allowed and spin-forbidden f–d transitions of Tb3+ ion, the bands at about 187 and 166 nm for the sample of Ba3BP3O12: Sm3+ have been considered as related to the charge transfer and the f–d transition of Sm3+, and the band at 146 nm for the sample of Ba3BP3O12: Gd3+ is assumed to be connected with charge transfer of the Gd3+ ion.
Co-reporter:Man-Rong Li, Wei Liu, Ming-Hui Ge, Hao-Hong Chen, Xin-Xin Yang and Jing-Tai Zhao
Chemical Communications 2004 (Issue 11) pp:1272-1273
Publication Date(Web):29 Apr 2004
DOI:10.1039/B402966F
The title compound, synthesized in a water-free flux under mild conditions (513 K in autoclaves), exhibits a zeolite-like and chiral open-framework related to gismondine (GIS).
Co-reporter:Wei Liu, Man-Rong Li, Hao-Hong Chen, Xin-Xin Yang and Jing-Tai Zhao
Dalton Transactions 2004 (Issue 18) pp:2847-2849
Publication Date(Web):11 Aug 2004
DOI:10.1039/B407341J
The title zincoborophosphate was synthesized hydrothermally from a mixture of ZnO, B2O3, H3PO4 and the structure-directing amine, DETA. Its crystal structure contains helices made up of corner-sharing BO4 and PO4 tetrahedra, which interconnected with ZnO4 tetrahedra to form a three dimensional structure with the CZP topology. The amine and water molecules occupy the free thread of the helices and the center of the channels, respectively. Thermal stability investigations show that this new compound can be dehydrated at 423 K and the product is stable up to 723 K. Furthermore, the as-synthesized title compound and its dehydration product are luminescent, each with a similar broad band between 350 and 550 nm, but the emission of the latter is about three times more intense than that of the former.
Co-reporter:Wei Liu, Xin Xin Yang, Hao Hong Chen, Ya Xi Huang, Walter Schnelle, Jing Tai Zhao
Solid State Sciences 2004 Volume 6(Issue 12) pp:1375-1380
Publication Date(Web):December 2004
DOI:10.1016/j.solidstatesciences.2004.07.035
A nickel diphosphate with mixed cations, Na(NH4)[Ni3(P2O7)2(H2O)2] with a layered structure has been synthesized under hydrothermal conditions for the first time and characterized by single crystal X-ray diffraction, IR spectroscope and magnetization measurements. The structure consists of cis- and trans-edge sharing NiO6 octahedral chains linked via P2O7 units to [Ni3P4O16]2− layers. The ammonium and sodium cations are alternately located in the interlayer spaces. The mixed cations play an important role in the structural formation of this layered compound, leading to a new layer-stacking variant. The magnetic susceptibility obeys a Curie–Weiss law with μeffμeff of 3.32 μBμB, showing the Ni2+ character and weak antiferromagnetic interactions.
Co-reporter:Kai Guo, Zhen-Yong Man, Qi-Gao Cao, Hao-Hong Chen, Xiangxin Guo, Jing-Tai Zhao
Chemical Physics (28 February 2011) Volume 380(Issues 1–3) pp:
Publication Date(Web):28 February 2011
DOI:10.1016/j.chemphys.2010.12.006
The structural stability, chemical bonding, Mulliken populations, and charge-density distribution of REZnOSb (RE = La–Nd, Sm–Gd) were investigated by first-principles calculations. Unit cell parameters calculated by the generalized gradient approximation (GGA) are in better agreement with experimental results than those derived from the local density approximation (LDA). Binding energy comparisons indicate that the structural stability of REZnOSb decreases with the increment of the atomic number of the RE, as confirmed by X-ray diffraction (XRD) results. Semimetal or narrow band-gap semiconductor behaviors are found for selected REZnOSb. Moreover, chemical bonding analysis shows that there exist considerable polar covalent interactions between the participating atoms. It also reveals that the [ZnSb] layers receive some electrons from the [LaO] layers (donor) as an electrons acceptor and holes transport tunnel. The covalent interactions between the [ZnSb] and [LaO] layers, which are enhanced by 4f-electrons of the RE, are supposed to improve the electrical transport properties.Graphical abstractThe structure stability of REZnOSb decreases with varying rare-earth from La to Gd because of the increased binding energy.Research highlights► As increasing the atomic number of the RE, the structural stability of REZnOSb decreases. ► Varying the rare-earth elements from La to Gd, the covalent interactions between [ZnSb] and [LaO] layer are enhanced by 4f-electrons. ► The electrical transport properties of REZnOSb could be improved using the large atomic number of the RE.
Co-reporter:Zhi-Jun Zhang, Hong Wang, Guan-Qin Hu, Hao-Hong Chen, Xin-Xin Yang, Jing-Tai Zhao
Journal of Crystal Growth (15 April 2010) Volume 312(Issue 9) pp:1577-1580
Publication Date(Web):15 April 2010
DOI:10.1016/j.jcrysgro.2010.01.035
Single crystals of Ba3BP3O12 with size of 10×8×2 mm3 have been grown by the top-seeded solution growth (TSSG) method using BPO4–NaF mixture as the flux. The crystals were characterized by X-ray powder diffraction, field emission scanning electron microscopy (FE-SEM) and transmittance spectrum. Ba3BP3O12 single crystal exhibits wide transparency in the range 250–800 nm. The preparation process of starting materials and the effect of flux on the crystal growth were discussed.
Co-reporter:Xin-Yuan Sun, Da-Guo Jiang, Wen-Feng Wang, Chun-Yan Cao, Yu-Nong Li, Guo-Tai Zhen, Hong Wang, Xin-Xin Yang, Hao-Hong Chen, Zhi-Jun Zhang, Jing-Tai Zhao
Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment (11 July 2013) Volume 716() pp:90-95
Publication Date(Web):11 July 2013
DOI:10.1016/j.nima.2013.03.036
•Glass-forming region of B2O3–GeO2–Gd2O3 ternary system are determined.•Radioluminescence response from transition-metal doped B2O3–GeO2–Gd2O3 glasses.•Radioluminescence response from rare-earth doped B2O3–GeO2–Gd2O3 glasses.•Emission peak position and decay time can be tuneable by incorporating various activators.Novel B2O3–GeO2–Gd2O3 ternary scintillating glasses doped with 1 mol% rare-earth and transition-metal activators were synthesized by melt-quenching method. Their transmittance, photoluminescence (PL) and X-ray excited luminescence (XEL) spectra were investigated. The results suggest that a high content of Gd2O3 is of significance for designing dense glass with density of 6.0 g/cm3. And energy transfer from Gd3+ to the incorporated activators can be realized in the borogermanate glasses. The emission position and decay time can be efficiently tuned by incorporating various kinds of activators. All results imply the developed borogermanate scintillating glass is potential for scintillating fields.
Co-reporter:Kai Guo, Zhen-Yong Man, Xiao-Jun Wang, Hao-Hong Chen, Mei-Bo Tang, Zhi-Jun Zhang, Yuri Grin and Jing-Tai Zhao
Dalton Transactions 2011 - vol. 40(Issue 39) pp:NaN10013-10013
Publication Date(Web):2011/09/06
DOI:10.1039/C1DT10721F
An efficient route to construct a three-dimensional crystal structure is stacking of two-dimensional building blocks (2D-BBs). The crystal structures of potential thermoelectric compounds REOZnSb (RE = La, Ce, Pr, Nd) were virtually constructed from insulating [REO] and conducting [ZnSb] layers. Further optimizations performed by means of first-principles calculations show that REOZnSb should exhibit semimetal or narrow band-gap semiconductor behaviors, which is a prerequisite for high thermoelectric efficiency. The analysis of the electron localizability indicator for LaOZnSb reveals mostly covalent polar interactions between all four kinds of atoms. The electron density yields completely balanced ionic-like electronic formula La1.7+O1.2−Zn0.4+Sb0.9−. Furthermore, the samples of REOZnSb have been synthesized via solid-state reaction, and their crystal structures were confirmed by powder X-ray diffraction. The differences in cell parameters between the theoretically optimized and the experimental values are smaller than 2%. The temperature dependence of the magnetic susceptibility shows that LaOZnSb is diamagnetic above 40 K, whereas CeOZnSb, PrOZnSb and NdOZnSb are Curie–Weiss-type paramagnets. Electrical conductivity and Seebeck effect measurements indicate that REOZnSb are p-type semiconductors. A considerably high Seebeck coefficient and low thermal conductivity were obtained for pure LaOZnSb, but its low electrical conductivity leads to a small ZT. The high adjustability of the crystal structure as well as properties by optimization of the chemical composition in the compounds REOZnSb provide good prospects for achieving high thermoelectric efficiency.
Co-reporter:Jiao Wang, Zhi-Jun Zhang, Jing-Tai Zhao, Hao-Hong Chen, Xin-Xin Yang, Ye Tao and Yan Huang
Journal of Materials Chemistry A 2010 - vol. 20(Issue 48) pp:NaN10900-10900
Publication Date(Web):2010/10/18
DOI:10.1039/C0JM01814G
Three-dimensional (3D) Y2WO6 and Y2WO6: Ln3+ microspheres with novel controllable morphology have been obtained by the hierarchical self-assembly via a hydrothermal synthesis route with a subsequent heat treatment. The amount of citric acid and polyvinylpyrrolidone (PVP) play crucial roles in the controlling of the morphologies. Hollow, core/shell as well as waxberry-shape Y2WO6 microspheres can be prepared in different reaction systems under the same facile hydrothermal conditions. Metastable phases of the samples form when they are crystallized at low temperature, which transfer to the thermodynamically stable counterpart above 1100 °C. This phase transformation is irreversible. The mechanism of reaction and self-assembly evolution process are proposed. The as-prepared Y2WO6:Ln3+ (Ln = Eu, Er, Sm, and Dy) samples show strong multi-color visible light emission under ultraviolet-visible light excitation. Compared with the monoclinic one, this metastable Y2WO6: Eu3+ phase exhibits different luminescent properties. Due to multi-color luminescent properties, these Ln3+-doped (Ln = Eu, Er, Sm, and Dy) metastable Y2WO6 morophologies controllable microspherical samples may be promising for further fundamental research and find applications in color displays.
Co-reporter:Hui Zhang, Michael Baitinger, Mei-Bo Tang, Zhen-Yong Man, Hao-Hong Chen, Xin-Xin Yang, Yi Liu, Ling Chen, Yuri Grin and Jing-Tai Zhao
Dalton Transactions 2010 - vol. 39(Issue 4) pp:NaN1104-1104
Publication Date(Web):2009/09/25
DOI:10.1039/B916346H
The thermoelectric performance of EuZn2Sb2 and EuCd2Sb2 was optimized by mixed occupation of the transition metal position. Samples in the solid solution Eu(Zn1−xCdx)2Sb2 with the CaAl2Si2-type crystal structure (space group m1) were prepared from the elements for compositions with x = 0, 0.1, 0.3, 0.5 and 1. The thermoelectric properties were investigated after densification of the products by spark plasma sintering (SPS). The samples show low electrical resistivity, high thermopower and a low lattice thermoconductivity. The highest ZT value of 1.06 at 650 K is obtained for x = 0.1.
Co-reporter:Li-Li Yu, Jun-Jie Zhu and Jing-Tai Zhao
Journal of Materials Chemistry A 2014 - vol. 2(Issue 24) pp:NaN9360-9360
Publication Date(Web):2014/04/22
DOI:10.1039/C4TA00155A
Hierarchical porous β-MnO2 nanoflowers self-assembled by ultrathin (thickness less than 10 nm) nanoplates have been successfully fabricated at room temperature. Because of its high specific surface area (267 m2 g−1) and proper pore size distributions (average pore size, ca. 5.9 nm), the obtained 3D nanomaterials achieve enhanced capacitance as high as 296.3 F g−1 at a scanning rate of 2 mV s−1, which is ∼20 times of those of the traditionally prepared nanostructural β-MnO2 (e.g. 1D hollow β-MnO2 nanorods with ∼14.9 F g−1). Furthermore, it has an appreciable ability to deliver large energy densities at high rates (67.4% capacitive retention). The comparable property with α-MnO2 indicates that such low-cost porous β-MnO2 nanoflowers may also be a very promising candidate material for supercapacitors besides lithium battery material.
