Co-reporter:Fang Xu, Yulong Liao, Dainan Zhang, Tingchuan Zhou, Jie Li, Gongwen Gan, and Huaiwu Zhang
Inorganic Chemistry April 17, 2017 Volume 56(Issue 8) pp:4512-4512
Publication Date(Web):March 27, 2017
DOI:10.1021/acs.inorgchem.7b00111
LiZn ferrite ceramics with high saturation magnetization (4πMs) and low ferromagnetic resonance line widths (ΔH) represent a very critical class of material for microwave ferrite devices. Many existing approaches emphasize promotion of the grain growth (average size is 10–50 μm) of ferrite ceramics to improve the gyromagnetic properties at relatively low sintering temperatures. This paper describes a new strategy for obtaining uniform and compact LiZn ferrite ceramics (average grains size is ∼2 μm) with enhanced magnetic performance by suppressing grain growth in great detail. The LiZn ferrites with a formula of Li0.415Zn0.27Mn0.06Ti0.1Fe2.155O4 were prepared by solid reaction routes with two new sintering strategies. Interestingly, results show that uniform, compact, and pure spinel ferrite ceramics were synthesized at a low temperature (∼850 °C) without obvious grain growth. We also find that a fast second sintering treatment (FSST) can further improve their gyromagnetic properties, such as higher 4πMs and lower ΔH. The two new strategies are facile and efficient for densification of LiZn ferrite ceramics via suppressing grain growth at low temperatures. The sintering strategy reported in this study also provides a referential experience for other ceramics, such as soft magnetism ferrite ceramics or dielectric ceramics.
Co-reporter:Xin Huang, Huaiwu Zhang, Yuanming Lai, Jie Li
Journal of Alloys and Compounds 2017 Volume 726(Volume 726) pp:
Publication Date(Web):5 December 2017
DOI:10.1016/j.jallcom.2017.07.292
•The Q × f values of Ni1-xZnxTiNb2O8 ceramics were increased when Zn content increased.•The Ni0.3Zn0.7TiNb2O8 ceramics obtained a near zero τf values of −4.63 ppm/°C.•Addition of B2O3-ZnO glass lowered sintering temperature of Ni0.3Zn0.7TiNb2O8 ceramics to 950 °C.•A near zero τf values of −4.14 ppm/°C was obtained for Ni0.3Zn0.7TiNb2O8 ceramics at 950 °C.The low-loss Ni1-xZnxTiNb2O8 (x = 0.2–0.8) ceramics prepared by the solid state synthesis methods, effects of various Zn contents on phases, microstructures and microwave dielectric properties for Ni1-xZnxTiNb2O8 were researched systematically. With an increasing x value, both dielectric constant and temperature coefficient of resonant frequency (τf) of Ni1-xZnxTiNb2O8 ceramics were reduced. In particular, excellent dielectric properties of Ni0.3Zn0.7TiNb2O8 ceramics were obtained when it was sintered at 1060 °C (εr = 39.23, Q × f = 30089 GHz and τf = −4.63 ppm/°C). The B2O3-ZnO glass addition can greatly lower the sintering temperature of Ni0.3Zn0.7TiNb2O8 and keep considerably outstanding dielectric properties. Typically, the dense and temperature stabled Ni0.3Zn0.7TiNb2O8 ceramics could be obtained with 3 wt% B2O3-ZnO glass addition, and a fairly good microwave dielectric properties with εr = 34.3, Q × f = 20255 GHz and a near-zero τf = −4.14 ppm/°C were shown when it was sintered at 950 °C.Download high-res image (236KB)Download full-size image
Co-reporter:Yicheng Wang, Luo Wang, Huaiwu Zhang, Zhiyong Zhong, Dongliang Peng, Fei Ye, Feiming Bai
Journal of Alloys and Compounds 2016 Volume 667() pp:229-234
Publication Date(Web):15 May 2016
DOI:10.1016/j.jallcom.2016.01.165
•Nanogranular FeCo–Ti–O films with single or double permeability spectrum peaks.•Tunable ferromagnetic resonance frequency and absorption bandwidth up to 3 GHz.•A three-component structure with two magnetic phases embedded in amorphous matrix.A series of soft magnetic nanogranular FeCo–Ti–O films with different Ti contents were fabricated on Si substrates by co-sputtering. By adjusting the Ti content, it appears that the imaginary part of the permeability spectra of FeCo–Ti–O films changes from a single peak to double peaks then to a single peak. Frequency conversion ferromagnetic resonance (FMR) analysis evidences that double FMR peaks can be found in all three films, which were attributed to local anisotropy or two magnetic phases embedded in amorphous TiOx matrix. Structural and temperature dependent resistivity analysis support such three component microstructure. The overlapping double FMR peaks provide a wide absorption frequency band over 3 GHz, which is critical for the design of electromagnetic interference suppressor.
Co-reporter:Tianlong Wen, Dainan Zhang, Qiye Wen, Huaiwu Zhang, Yulong Liao, Qiang Li, Qinghui Yang, Feiming Bai and Zhiyong Zhong
Nanoscale 2015 vol. 7(Issue 11) pp:4906-4911
Publication Date(Web):16 Feb 2015
DOI:10.1039/C4NR07489K
Inverted pyramid hole arrays were fabricated by photolithography and used as templates to direct the growth of colloidal nanoparticle assemblies. Cobalt ferrite nanoparticles deposit in the holes to yield high quality pyramid magnetic nanoparticle assembly arrays by carefully controlling the evaporation of the carrier fluid. Magnetic measurements indicate that the pyramid magnetic nanoparticle assembly arrays preferentially magnetize perpendicular to the substrate.
Co-reporter:Yulong Liao, Dainan Zhang, Qi Wang, Tianlong Wen, Lijun Jia, Zhiyong Zhong, Feiming Bai, Longhuang Tang, Wenxiu Que and Huaiwu Zhang
Journal of Materials Chemistry A 2015 vol. 3(Issue 27) pp:14279-14283
Publication Date(Web):02 Jun 2015
DOI:10.1039/C5TA02799C
Anodic growth of TiO2 nanotube (NT) arrays has been proved to be very promising for energy conversion applications, e.g. in photovoltaic devices and fuel cells. However, disordered “nano-grass” layers were always found on the top of the anodic TiO2 NT arrays. In this paper, we demonstrate a novel and simple method using a micromechanical cleavage technique to peel off the disordered nanograss layer. Using this method, ∼1 × 1.5 cm−2 of uncapped TiO2 NT arrays with a high-aspect ratio can be easily obtained. The results further indicate that the treatment can improve the photovoltaic and photochemical performances. After the treatment, the conversion efficiency (η) of the dye sensitized solar cells (DSSCs) increased by 29.3%. This work facilitates the growth and applications of high aspect-ratio anodic TiO2 NT arrays in related devices and systems.
Co-reporter:Tingchuan Zhou
The Journal of Physical Chemistry C 2015 Volume 119(Issue 23) pp:13207-13214
Publication Date(Web):May 18, 2015
DOI:10.1021/jp512608z
NiZn ferrite nanoparticles (2–20 wt %) of composition Ni0.4Zn0.6Fe2O4 were introduced into LiZnTi ferrite of composition Li0.42Zn0.27Ti0.11Fe2.2O4 and sintered at a temperature of 920 °C for 2 h, well below that of the Ag melting point. Here, LiZnTi ferrites were prepared by a solid-state reaction method, and NiZn ferrite nanoparticles were fabricated by a hydrothermal chemical technique at 180 °C. A low ferromagnetic resonance (FMR) line width, low coercivity, and high magnetic moment were achieved after refinement of the heat treatment conditions of the mixture. Riveted full profile refinement of the X-ray powder diffraction patterns and analysis of Mössbauer spectra were employed to study the structure and caption distribution. The results confirm a pure spinel phase after processing. A narrow FMR line width of 152.5 Oe, a reduced coercivity of 132.9 A/m, and an improved saturation magnetization of 74.23 emu/g were obtained by way of the addition of 8 wt % NiZn ferrite nanoparticles.
Co-reporter:Yulong Liao, Jin Zhang, Weiguo Liu, Wenxiu Que, Xingtian Yin, Dainan Zhang, Longhuang Tang, Weidong He, Zhiyong Zhong, Huaiwu Zhang
Nano Energy 2015 Volume 11() pp:88-95
Publication Date(Web):January 2015
DOI:10.1016/j.nanoen.2014.09.034
Quantum dot-sensitized solar cells (QDSSCs) are one kind of promising photovoltaic devices for harvesting solar energy. Previous reports have studied various photoanode materials in order to achieve a high photoelectric performance, while little attention has been paid to the electrolyte system inside the QDSSCs. In this report, a polysulfide (S2−/Sx2−) electrolyte system was investigated and optimized based on a CdS quantum dot/ZnO nanowire solar cell and a CdSe/CdS co-sensitized QDSSC. Water–methanol mixed solution was taken as the solvent for this polysulfide electrolyte, considering simultaneously the penetration ability and the ion dissociation of the electrolyte. Electrochemical impedance spectra (EIS) measurement was used to investigate the impedance of the electrons recombination with the electrolyte at the photoanode/electrolyte interface. With the measured efficiency of the CdS-QDSSCs, the optimal composition of the electrolyte can be obtained. The work facilitates the development of highly-efficient electrolyte in the general field of quantum dot-sensitized solar cells.
Co-reporter:Sha-Sha Ke, Hai-Feng Lü, Hua-Jun Yang, Yong Guo, Huai-Wu Zhang
Solid State Communications 2014 Volume 184() pp:12-16
Publication Date(Web):April 2014
DOI:10.1016/j.ssc.2013.12.025
Highlights•We examine the noise cross correlations between the tunneling currents through two indirectly coupled mesoscopic conductors.•For single level in the connected channel, we could judge the corporate or competitive correlation through the signs of other two correlations.•The correlation relationship becomes complex and unpredictable when there are several energy levels in the connected conductor.We analyze the current noise cross correlations (CCs) between the currents through two mesoscopic conductors without direct interaction, where a connected conductor is capacitively coupled with them. We demonstrate that the CCs between two indirectly coupled conductors do not decrease when the device works at low bias voltages. More importantly, the competitive or cooperative relationship between two currents is also unpredictable, which depends on the level configuration and the property of the connected conductor. Even when the CCs between directly coupled channels vanish, the tunneling currents through two indirectly coupled conductors are still strongly correlated.
Co-reporter:Yulong Liao, Huaiwu Zhang, Wenxiu Que, Peng Zhong, Feiming Bai, Zhiyong Zhong, Qiye Wen, and Wenhao Chen
ACS Applied Materials & Interfaces 2013 Volume 5(Issue 14) pp:6463
Publication Date(Web):July 1, 2013
DOI:10.1021/am401869e
TiO2 films consisting of single-crystal anatase nanoparticles with exposed {001} facets were fabricated from anodized TiO2 nanotube arrays. The films’ photocatalytic activities were further activated and then enhanced (∼2.5 times) by removing F– from the {001} facets. This study indicates that fluorine-free crystal surfaces are of great importance for the application of such kinds of single-crystal TiO2 nanoparticle films with exposed {001} facets in related areas.Keywords: anatase; photocatalyst panel; single crystal; TiO2 film; {001} facets;
Co-reporter:Lin Cheng, Peng Liu, Shi-Xian Qu, Huai-Wu Zhang
Journal of Alloys and Compounds 2013 Volume 581() pp:553-557
Publication Date(Web):25 December 2013
DOI:10.1016/j.jallcom.2013.06.133
•The AWO4 nanopowders with a single phase were synthesized by HEBM for 30 min.•The average particle size of the milled powders is reduced to 120–180 nm for 30 h.•AWO4 ceramics were well sintered at relatively low temperatures of 900–1000 °C.•Samples have dense microstructures and excellent microwave dielectric properties.The AWO4 (A = Ca, Sr, Ba) compounds with scheelite structure were synthesized by high energy ball milling for 30 min and the average particle size was reduced to about 120 nm after milling 30 h. AWO4 ceramics were well sintered at relatively low temperatures of 900–1000 °C, 200–400 °C lower than those required by a conventional solid state reaction technique. The samples of CaWO4, SrWO4, and BaWO4 ceramics have dense microstructures and excellent microwave dielectric properties, ɛr = 10.7, 8.6, 8.4; Q × f = 62,100 GHz, 57,500 GHz, 58,800 GHz; and τf = −48 ppm/°C, −52 ppm/°C, −64 ppm/°C, respectively.
Co-reporter:Jie LI, Huaiwu ZHANG, Qiang LI, Yuanxun LI, Guoliang YU
Journal of Rare Earths 2013 Volume 31(Issue 10) pp:983-987
Publication Date(Web):October 2013
DOI:10.1016/S1002-0721(13)60017-4
La-Co substituted M-type barium ferrites (BaM) were prepared by traditional solid state method and sintered at low temperature (1173 K). X-ray diffraction (XRD), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) were employed to investigate the influence of La-Co on the structure and magnetic properties of the samples. By sintering at 1173 K for 6 h in air, single phase M-type barium ferrites with chemical composition of Ba(LaCo)xFe12−2xO19 (x=0.0−0.5) were formed. M-H curves showed that the magnetic properties of barium ferrites were obviously effected by La-Co substitution. The saturation magnetization (Ms) and coercivity (Hc) reached the maximum value of 65.15 Am2/kg and 4165 Oe, respectively. This behavior was attributed to the sites of La-Co substitutions and the particles size. SEM revealed that the shape of ferrite particles was influenced by La-Co substitution.Variation of Ms and Hc with different sintering temperatures in the La-Co substituted samples (a) 1173 K for 6 h; (b) 1173 K for 4 h
Co-reporter:Zhi-Fen Fu, Peng Liu, Xiao-Ming Chen, Jian-Li Ma, Huai-Wu Zhang
Journal of Alloys and Compounds 2010 Volume 493(1–2) pp:441-444
Publication Date(Web):18 March 2010
DOI:10.1016/j.jallcom.2009.12.122
The effects of high-energy ball milling and subsequent calcinations on the mixture of MgO and Nb2O5 were investigated. It was found that the formation temperature of the single-phase Mg4Nb2O9 powders had a consanguineous connection with milling time, calcinations temperature and dwell time. With increasing milling time, calcinations temperature and dwell time, the qualitative concentration of Mg4Nb2O9 phase increased. Pure Mg4Nb2O9 nanopowders with average particle size of 72.5 nm were primary synthesized at 900 °C for 3 h from 60 h powders. The Mg4Nb2O9 ceramics with almost full density and an excellent microwave dielectric properties (ɛr = 12.6, Q × f = 175,810 GHz) were obtained after annealing at 1200 °C from the milled 60 h powders.
Co-reporter:Peng Liu, Jianli Ma, Ling Meng, Jun Li, Lanfang Ding, Jingliang Wang, Huai-Wu Zhang
Materials Chemistry and Physics 2009 Volume 114(2–3) pp:624-628
Publication Date(Web):15 April 2009
DOI:10.1016/j.matchemphys.2008.10.008
The 100(1 − y) wt%Ba1−xSrxTiO3–100y wt%Mg2TiO4 (BST-MT, 0.45 ≤ x ≤ 0.6, 0.3 ≤ y ≤ 0.7) composite ceramics were fabricated by mixing (Ba,Sr)TiO3 and Mg2TiO4 powders via a conventional ceramic processing technique. The sintering behavior, microstructures, and dielectric properties of composite ceramics were investigated. The dense BST-MT composite ceramics were obtained at a temperature range from 1350 to 1430 °C without forming the impurity phases. By adjusting the relative content of two components and the Ba/Sr ratio in (Ba,Sr)TiO3, an optimum ceramic composite with dielectric constant ∼76.5, loss tangent ∼0.0007 at 10 kHz and 20 °C, dielectric tunability ∼10.2% under a dc electric field of 20 kV cm−1 and good temperature stability of dielectric constant was attained.
Co-reporter:Sha-Sha Ke, Hai-Feng Lü, Hua-Jun Yang, Xiao-Tao Zu, Huai-Wu Zhang
Solid State Communications 2009 Volume 149(45–46) pp:2102-2105
Publication Date(Web):December 2009
DOI:10.1016/j.ssc.2009.08.010
We extend the bond-operator mean-field theory to study the rung singlet phase and its phase boundary, the triplet excitation, and the spin gap of the spin–orbital models with four-spin exchanges. The theory gives a well description of the rung singlet phase and phase boundaries in two-dimensional (2D) and three-dimensional (3D) cases are predicted. It is shown that consideration of the ring exchange suppresses the excitation spectrum and decreases the spin gap. For 2D and 3D spin–orbital models, positive ring and leg coupling tend to collaborate with each other to break the rung singlet phase. On the boundary line Jleg=Jring
Co-reporter:Chunhong Mu, Huaiwu Zhang, Ying He, Peng Liu, Jian Shen
Materials Science and Engineering: B 2009 Volume 162(Issue 3) pp:195-199
Publication Date(Web):15 June 2009
DOI:10.1016/j.mseb.2009.04.012
A new Fe3+ substituted CaCu3Ti4−xFexO12 (CCTFO, 0 ≤ x ≤ 0.2) ceramics prepared by solid-state reaction method has been systematically studied. Three new relaxation processes were discovered by means of dielectric properties spectra measurement. The first and second relaxation processes (I and II) were observed at room temperature for CCTFO (0 ≤ x ≤ 0.04), and the third relaxation process (III) appeared starting about 75 °C only for CCTFO (x = 0.01). These rare multiple dielectric relaxation processes urge us exploring the fascinating origin of giant dielectric constant in CaCu3Ti4−xFexO12 ceramics. Impedance measurement results showed that the resistivity of grains and grain boundaries increased while dielectric constant decreased dramatically in the frequency range of 1 kHz to 1 MHz with content x increasing. Based on the IBLC model, we can explain that relaxation process I origins from Maxwell–Wagner relaxation at grain boundaries. In the frequency range of occurring relaxation process II, dielectric constant decreased from 105 to 5 × 104 after surface polishing, which confirmed that the giant dielectric constant appearing at low frequency (<1 kHz) originated not only from the grain boundaries but also the surface layers in the new ceramics. For relaxation process III, permittivity plateau appears at lower frequency range starting from 100 Hz and high temperature (T ≥ 75 °C) may be relative to the concentration of localized charge carriers.
Co-reporter:H.W Zhang, Y.L Liu, Z.Y Zhong
Vacuum 2001 Volume 62(Issue 1) pp:1-6
Publication Date(Web):25 May 2001
DOI:10.1016/S0042-207X(00)00455-3
A microchip thin film transformer which is composed of an I-shaped [CoZrNb/SiOx]m magnetic layer and wound with Cu thin film coils fabricated by using a mask vacuum evaporation and sputtering composited process has been investigated. Comparing the CoZrNb core with [CoZrNb/SiOx]m core of thin film transformer, it is shown that the multilayer thin films have more advantages than a single magnetic layer in their of soft magnetic properties, especially the permeability (μ) and coercivity (Hc). The microchip transformer has a relatively high inductance of 0.4–1.0 μH for a ratio of primary turns to secondary coil turns of 3 : 1 and 3 : 2, and has a high Q value of 4–12. The thin film transformer can be operated in an integrated micro-switching converter at a frequency between 1 kHz and 10 MHz.
Co-reporter:H.W Zhang, Z.Y Zhong, Y.L Liu, H.C Wang
Vacuum 1999 Volume 55(3–4) pp:197-200
Publication Date(Web):1 December 1999
DOI:10.1016/S0042-207X(99)00150-5
A new thin film transformer which is composed of an E-shaped CoZrRe magnetic layer and wound with Cu thin film coils fabricated by using a mask vacuum evaporation process has been investigated. The ratio of primary coil turns to secondary coil turns is 3 : 1 and 3 : 2. The transformer has a relatively high inductance of 0.4–0.8 μH, and can be operated in an integrated micro-switching converter at frequencies between 100 KHz and 10 MHz.
Co-reporter:Yulong Liao, Dainan Zhang, Qi Wang, Tianlong Wen, Lijun Jia, Zhiyong Zhong, Feiming Bai, Longhuang Tang, Wenxiu Que and Huaiwu Zhang
Journal of Materials Chemistry A 2015 - vol. 3(Issue 27) pp:NaN14283-14283
Publication Date(Web):2015/06/02
DOI:10.1039/C5TA02799C
Anodic growth of TiO2 nanotube (NT) arrays has been proved to be very promising for energy conversion applications, e.g. in photovoltaic devices and fuel cells. However, disordered “nano-grass” layers were always found on the top of the anodic TiO2 NT arrays. In this paper, we demonstrate a novel and simple method using a micromechanical cleavage technique to peel off the disordered nanograss layer. Using this method, ∼1 × 1.5 cm−2 of uncapped TiO2 NT arrays with a high-aspect ratio can be easily obtained. The results further indicate that the treatment can improve the photovoltaic and photochemical performances. After the treatment, the conversion efficiency (η) of the dye sensitized solar cells (DSSCs) increased by 29.3%. This work facilitates the growth and applications of high aspect-ratio anodic TiO2 NT arrays in related devices and systems.
