Papers by Author: Qiu Xiang Liu

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Authors: Jun Bo Wu, Xin Gui Tang, Qiu Xiang Liu, Yan Ping Jiang
Abstract: (Pb1-xBax)ZrO3 (PBZ) ceramics for x = 0.10 were synthesized by the mixed oxide solid state reaction method. Phase transition was investigated by dielectric measurements in the temperature range from 27 to 350 °C at various frequencies. The permittivity of the solids corresponding to (Pb1-xBax) ZrO3 showed the maximum value of 10220 at x = 0.10 at the phase transition temperature. The maximum permittivity gradually increasing concentration up to x = 0.10. The ferroelectric hysteresis loop of the PBZ ceramics for x = 0.10 is displayed at room temperature and 0.2 Hz.
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Authors: Xiao Fang Cheng, Xin Gui Tang, Shao Gong Ju, Yan Ping Jiang, Qiu Xiang Liu
Abstract: The 0.94Bi0.5Na0.5TiO3-0.06BaTiO3 (abbreviated to BNT-BT) powder and ceramic was synthesized by sol-gel process. The phase structure and dielectric properties of the ceramics were investigated. The ceramic was sintering at 1000-1100 degree C for 2-4 h in air atmosphere, and the X-ray diffraction (XRD) results revealed that the samples was pure perovskite-type phase. The Curite temperature of BNT-BT ceramics was high up to 348 degree C. The temperature dependence of dielectric permittivity and loss revealed there were two phase transitions, which were from ferroelectric (tetragonal) to anti-ferroelectric (rhombohedral) and anti-ferroelectric to paraelectric (cubic) in BNT-BT ceramics. Diffuse phase transitions were observed in BNT and BNT-BT ceramics and the Curie-Weiss Exponent (CWE) were nearly 2.
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Authors: Shao Gong Ju, Xin Gui Tang, Jun Bo Wu, Yan Ping Jiang, Qiu Xiang Liu
Abstract: In this work, effect of low sintering temperature and time on the new lead-free perovskite (Ba0.7Ca0.3)TiO3-Ba(Zr0.2Ti0.8)O3 (BCZT) solid solution ceramics have been investigated. X-ray diffraction (XRD) was used to understand the phase transition of the BCZT during heating. The Curie temperature decreased nonlinearly 43 K in BCZT ceramics. Diffuse phase transitions were observed in BCZT ceramics and the Curie-Weiss exponent (CWE) was nearly 2. The dielectric permittivity versus temperature characteristics and the γ in the modified Curie-Weiss law, as a function of the dc bias field was obtained for BCZT ceramics. The fitting of parameters (Tm vs. f ) have close agreement with the data of Vogel-Fulcher’s relationship.
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Authors: Yan Zou, Qiu Xiang Liu, Yan Ping Jiang, Xin Gui Tang
Abstract: Bi3.4Nd0.6Ti3O12 (BNT) thin films have been prepared on Si (100) substrate by RF magnetron sputtering method. The crystalline structures were studied by X-ray diffraction. The surface of the films have been observed by SEM. The reflectivity was measured by n & k Analyzer 2000 with the wavelength from 190 to 900 nm. The optical constant, thickness and the forbidden band gap were fitted. The results showed that with the annealing temperatures raised from 600 to 750 °C, the reflectivity index decreased from 2.224 to 2.039, and the forbidden band gap decreased from 3.19 to 2.99 eV. The possible mechanism of the effect of annealing temperature on the optical properties was discussed.
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Authors: Tie Dong Cheng, Xin Gui Tang, Shu Juan Kuang, Nan Ding, Yan Ping Jiang, Qiu Xiang Liu
Abstract: Lead strontium zirconate titanate (Pb0.92Sr0.08)(Zr0.65Ti0.35)O3 (PSZT) thin films were grown on Pt (111)/Ti/SiO2/Si(100) substrates using a simple sol-gel method. X-ray diffraction studies confirmed that all the PSZT films undergone various thermal process show highly preferred (001)-orientation. On the surface image of the thin film, many clusters are found, which are composed by grains in size of 0.5-0.8 mm. Between the clusters, the nano-size grain is about 50-80 nm. The root mean square (RMS) roughness of the film surfaces is 5.1 nm. PSZT thin film exhibit excellent ferroelectric behavior, demonstrated by reproducible hystersis loops with high remnant polarization (Pr =49 μC cm-2) and relative low coercive field (Ec=53.5 kV cm-1). The pyroelectric coefficients (p) were measured, at 26 °C, the p=215 mC m-2 K-1 for PSZT films. The dielectric properties as well as phase transition behavior were characterized and a ferroelectric to paraelectric transition were found in the vicinity of 196 °C.
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Authors: L.L. Li, Qiu Xiang Liu, Yan Zou, Xin Gui Tang, Yan Ping Jiang
Abstract: Bi0.9Nd0.1FeO3 (BNFO) films were deposited on Si (100) and (La,Sr)(Al,Ta)O3 (100) (LAST) substrate by radio frequency (RF) magnetron sputtering method respectively. The structure,morphology and magnetic properties were studied. X-ray diffraction (XRD) result indicates that the BNFO films on different substrate adopted different orientation. Cross-section scanning electron microscopy shows that the film thickness is 145 nm.Magnetic properties measurement shows that the film on Si(100) substrate has the larger saturation magnetization (Ms) of 3 686 emu/cm3, while the Ms value of the BNFO films on LSAT(100) substrate is only 1 213 emu/cm3.
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Authors: Shu Juan Kuang, Xin Gui Tang, Jun Bo Wu, Yan Ping Jiang, Qiu Xiang Liu
Abstract: Lead-free ceramics with the composition of Mn-doped Ba(Zr0.06Ti0.94)O3 xmol%MnO2 (BZT6-xMn, x=0, 1 and 2) have been synthesized by a mixed oxide process. Structure and micrograph characterization were examined using X-ray diffraction (XRD) and scanning electron microscopy (SEM), which revealed that all samples have the orthorhombic phase with dense and the uniform microstructure. The grain size of Mn-doped BZT6 ceramics decreased with increasing MnO2 doping. The effect of MnO2 doping on the dielectric and ferroelectric properties was also investigated. The maximum dielectric permittivity decreased dramatically with increasing MnO2 doping in the BZT6 ceramics. A peculiar double-hysteresis-like loop was observed. Mn ions as acceptor doping occupy the B site of ABO3 in the form of Mn2+ and Mn3+, which brought an increase in the oxygen vacancies concentration. The defect dipole model was explained the pinning mechanism.
354
Authors: Qiu Xiang Liu, Xin Gui Tang, Yan Ping Jiang, F. L. Dong
Abstract: Two kinds ceramics of pure CaCu3Ti4O12 (CCTO) and Sr/Mg doped (Ca0.25Cu0.75)0.5Sr0.5TiO3 + xMgO (x=0.01, 0.03, 0.05, 0.1, denoted as CCST-M-1, CCST-M-3, CCST-M-5, CCST-M-10, respectively) were prepared using the traditional solid phase reaction method. The dielectric properties were measured by HP 4194A Impedance/Gain-Phase Analyzer with the frequency range from 100 Hz to 1MHz. The temperature dependence of dielectric constant and loss tangent were measured for different frequencies. The variation relation of the critical temperature with the frequency was fitted theoretically which is in agreement with the Arrhenius law for pure CCTO. According to a variable power law to describe the paraelectric dielectric constant of ferroelectrics with diffuse phase transitions, the theoretical fitting was carried out for doped samples, and it was suggested that all doped samples exhibited the Debye-like relaxation. Among the doped and pure CCTO samples, CCST-M-1 was of the lowest dielectric loss at the whole measurement frequency, and whose I–V response curve was nonlinear suggesting a non-ohmic contact. The complex-impedance analysis results showed that the reduction in dielectric loss of CCST-M-1 sample can be attributed to the increase of grain boundary resistance. It is expect that these results are helpful to promote the CCTO-related materials to practical applications.
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Authors: Dong Ge Chen, Xin Gui Tang, Qiu Xiang Liu, Xiao Fang Cheng, Yan Zou
Abstract: Bismuth neodymium ferrite (Bi1-xNdxFeO3: BNFO; x=0, 0.025, 0.075, 0.125, 0.175) ceramics were prepared by a co-precipitation method and sintered at 800 °C, using nitrates as precursors. The crystal structure and dielectric properties of the samples were characterized by X-ray diffraction (XRD)and dielectric permittivity measurement at different temperatures and frequencies. XRD suggests that the impurity phases are weakened by suitably doping x=0.075. Dielectric spectra indicate that relaxation peaks below the Néel temperature which may be produced by the effect of grain boundaries and dipoles with heating vanish after doping Nd at the same content. Complex impedance spectra manifest that the doped samples are closer to Debye-type, and the impedance rises which will lead to low leakage current.
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Authors: Hui Fang Xiong, Tie Dong Cheng, X.G. Tang, Jian Chen, Qiu Xiang Liu
Abstract: (La0.7Sr0.3)MnO3 (LSMO) thin films were grown on Si (100) substrate by using pulsed laser deposition (PLD) process. Both structure and surface morphology of the films were investigated by X-ray diffraction (XRD) and atomic force microscopy (AFM). Furthermore, the chemical states and chemical composition of the films were determined by X-ray photoelectron spectroscopy (XPS) near the surface. From XRD, the results indicate that the films grown on Si (100) substrates have a single pseudocubic perovskite phase structure with a high (100) orientation. The XPS results show that La, Sr and Mn exist mainly in the forms of perovskite structure and a SrO layer was found on outermost surface. The films resistivity emeasured under room temperature is 6.4´10-4 W×cm.
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