Papers by Author: X.A. Mei

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Authors: X.A. Mei, Min Chen, W.K. An, Chong Qing Huang, J. Liu, A.H. Cai
Abstract: Pr-doped bismuth titanate (BixPryTi3O12: BPT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique, and the structures and Raman spectra of the films were investigated. XRD studies indicated that all of the BPT films consist of single phase of a bismuth-layered structure, showing a highly (117) oriented preferential growth with a minor fraction of (00l) orientation. For an increasing degree of Pr doping, Raman spectra studies revealed a substantial hardening of the vibration involving Bi atoms at the perovskite A site, whereas the Bi mode at the Bi2O2 layer is negligibly changed. From a comparison with a simple mass consideration, we identify a precise cation distribution, indicating a pronounced site selectivity of Pr ions for the A site for y ~ 1.2.
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Authors: C.Q. Huang, X.B. Liu, X.A. Mei, J. Liu
Abstract: The electrical properties of Er2O3-doped bismuth titanate,Bi4-xErxTi3O12 (BET) ceramics prepared by a conventional electroceramic technique were investigated. XRD analyses revealed Bi-layered perovskite structure in all samples. SEM micrographs showed randomly oriented and plate-like morphology. For the samples with x=0.4 and 1.0 the current-voltage characteristics exhibited negative differential resistance behaviors and their P-E hysteresis loops were characterized by large leakage current, whereas for the samples with x=0.6 and 0.8 the current-voltage characteristics showed simple ohmic behaviors and their P-E hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BET ceramic with x=0.8 were above 20μC/cm2 and 65KV/cm , respectively.
162
Authors: J.G. Liu, X.A. Mei, C.Q. Huang, J. Liu
Abstract: Bi2.9Pr0.9Ti2.97V0.03O12 (BPTV) ceramics were prepared by solid state reaction. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed plate-like grains with random orientation. BPTV caused a large shift of the Curie temperature ( TC ) of Bi4Ti3O12 (BIT) from 675°C to 385°C. The remanent polarization and the coercive field of the BLTV were 31μC/cm2 and 60kV/cm at an electric field of 100kV/cm, respectively. Furthermore, the dielectric permittivity and dissipation factor were 300 and 3.3×10-3 at 1MHz, at 1V and at room temperature, respectively. These ferroelectric properties of BPTV are superior to V-doped Bi4Ti3O12 (~20μC/cm2 and 80kV/cm) and (Sr, Ta)-doped Bi4Ti3O12 (~12μC/cm2 and 71kV/cm) ceramics. In addition, the dense ceramics of BPTV could be obtained by sintering at temperatures 100─200°C lower than those of the SrBi2Ta2O9 system.
166
Authors: Chong Qing Huang, M. Chen, X.A. Mei, Y.H. Sun, J. Liu
Abstract: Bi2WTi3O12 ceramics are fabricated by conventional solid-state reaction process. XRD analysis reveals that Bi2WO6 is the main phase and Bi4Ti3O12 is the second phase. With increasing temperature the sample first appears metallic behavior, then strong electrical fluctuations above 100°C, and finally exhibits stable nonlinear properties characterized by semiconductivity above 300°C at low field (E ≤ 100V/mm). The Arrhenius law for electrical conductivity by thermal activation is not suitable to explain the anomalous results. Based on the phase transition of tungsten trioxide from room temperature to about 300°C, the electrical properties of Bi2WTi3O12 ceramics can be explained.
238
Authors: X.B. Liu, X.A. Mei, C.Q. Huang, J. Liu
Abstract: The electrical properties of Gd2O3-bismuth titanate (Bi4-xGdxTi3O12) prepared by a conventional ceramic technique have been investigated. At applied d.c. field below 200V/mm, the current-voltage curve of Gd-doped sample exhibits a simple ohmic behavior. The impedance spectrum of Gd-doped sample indicates that consist of semiconducting grain and moderately insulating grain boundary regions. XRD, SEM and EPMA analyses reveal crystalline phase characterized by a Bi-layered perovskite structure of Bi4Ti3O12 and the distribution of every element is uniform. Gd-doped sample exhibit randomly oriented and plate-like morphology.
182
Authors: Y.H. Cai, X.A. Mei, Min Chen, K.L. Su, W.K. An, J. Liu
Abstract: The electrical properties of Bi3.25Dy0.75Ti3O12 (BDT) and Bi3.25Gd0.75Ti3O12 (BGT) ceramics were investigated. The current-voltage curve of the BGT sample exhibits a negative differential resistance behavior, whereas that of the BDT sample exhibits a simple ohmic behavior. The impedance spectrum of the BDT and BGT samples indicate that both consist of semiconducting grain and moderately insulating grain boundary regions. XRD, SEM and EPMA analyses reveal crystalline phase characterized by a Bi-layered perovskite structure of Bi4Ti3O12 and the distribution of every element is uniform. Both BDT and BGT samples exhibit randomly oriented and plate-like morphology.
88
Authors: Min Chen, X.A. Mei, Rui Fang Liu, C.Q. Huang, J. Liu
Abstract: The electrical properties of Sm-doped bismuth titanate,Bi4-xSmxTi3O12 (BST) ceramics prepared by a conventional electroceramic technique were investigated. XRD analyses revealed Bi-layered perovskite structure in all samples. The P-V hysteresis loops of samples with x=0.4 and 1.2 were characterized by large leakage current, whereas for samples with x=0.6 and 0.8 the P-E hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BST ceramic with x=0.8 were above 20μC/cm2 and 60KV/cm , respectively.
154
Authors: S. Chen, A.H. Cai, X.A. Mei, Chong Qing Huang, W.K. An, Min Chen
Abstract: Sm-doped bismuth titanate and random oriented Bi4-xCexTi3O12 (BCT) thin films were fabricated on Pt/Ti/SiO2/Si substrates rf magnetron sputtering technique. The structures and the ferroelectric properties of the films were investigated. Ce doping leads to a marked improvement in the remanent polarization (Pr) and the coercive field (Ec). At the applied electric field of 100 kV/cm, Pr and Ec of the BCT (x = 0.8) film annealed at 650 oC are 20.5 μC/cm2 and 60 KV/cm, respectively. However, after 3 × 1010 switching cycles, 20% degradation of 2Pr is observed in the film.
91
Authors: Min Chen, X.A. Mei, A.H. Cai, J. Liu, Chong Qing Huang
Abstract: Dy2O3-doped bismuth titanate (Bi4-xDyxTi3O12: BDT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique, and the structures and ferroelectric properties of the films were investigated. XRD studies indicated that all of BDT films consisted of single phase of a bismuth-layered structure with well-developed rod-like grains. The remanent polarization (Pr) and coercive field (Ec) of the BDT Film with x = 0.8 were 20 μC/cm2 and 60 KV/cm, respectively. After 3 × 1010 switching cycles, 20% degradation of Pr is observed in the film.
206
Authors: Min Chen, X.A. Mei, J. G. Liu, J. Liu, Chong Qing Huang
Abstract: The electrical properties of Eu-doped bismuth titanate,Bi4-xEuxTi3O12 (BET) ceramics prepared by a conventional electroceramic technique were investigated. XRD analyses revealed Bi-layered perovskite structure in all samples. SEM micrographs showed randomly oriented and plate-like morphology. For the samples with x=0.4 and 1.0 the current-voltage characteristics exhibited negative differential resistance behaviors and their P-V hysteresis loops were characterized by large leakage current, whereas for the samples with x=0.6 and 0.8 the current-voltage characteristics showed simple ohmic behaviors and their P-E hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BST ceramic with x=0.8 were above 16μC/cm2 and 70KV/cm , respectively.
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