Papers by Author: J. Liu

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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: Min Chen, Y.H. Sun, K.L. Su, J. Liu, S. Chen, Z.M. Wan
Abstract: Pr6O11-doped bismuth titanate and random oriented BixPryTi3O12 ( y = 0.3, 0.6, 0.9, 1.2) thin films were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed rod-like grains with random orientation. Pr doping into BIT caused a shift of the Curie temperature (TC) of the BIT from 675°C to 578 , 517, 398 , and 315oC for the films with y = 0.3, 0.6, 0.9, and 1.2, respectively. The experimental results indicated that Pr doping into BIT result in a remarkable improvement in dielectric properties. Raman analysis shows that Pr3+ and Pr4+ ions substitution only appears in A-sit.
155
Authors: Min Chen, W.K. An, A.H. Cai, Chong Qing Huang, K.L. Su, J. Liu
Abstract: The electrical properties and Microstructures of Tb-doped bismuth titanate (Bi3.3Tb0.6Ti3O12) ceramic were investigated. XRD analyses revealed that the sample had Bi-layered perovskite structure. SEM micrographs showed randomly oriented and plate-like morphology. The remanent polarization (Pr) and coercive field (Ec) of Bi3.3Tb0.6Ti3O12 ceramic are above 25 μC/cm2 and 80 KV/cm, respectively.
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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: 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, 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: X.A. Mei, Min Chen, K.L. Su, A.H. Cai, J. Liu, Wei Ke An, Yong Zhou, M. Jia
Abstract: Eu2O3-doped bismuth titanate (Bi1-xEuxTi3O12: BET) thin films with random oriention 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 BET films consisted of single phase of a bismuth-layered structure with well-developed rod-like grains. For samples with x=0.0 , 0.25, 1.0 and 1.25, I-E characteristics exhibited negative differential resistance behaviors and their ferroelectric hysteresis loops were characterized by large leakage current, whereas for samples with x=0.5 and 0.75, I-E characteristics were simple ohmic behaviors and their ferroelectric hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization (Pr) and coercive field (Ec) of the BET Film with x=0.75 were above 30μC/cm2 and 85KV/cm , respectively.
197
Authors: X.B. Liu, Y.H. Sun, Min Chen, Chong Qing Huang, J. Liu, Z.M. Wan
Abstract: The electrical properties of Gd-doped bismuth titanates (Bi3.25Gd0.75Ti3O12, BGT) prepared by a conventional ceramic technique have been investigated. At applied d.c. field below 200V/mm, the current-voltage curve of the BGT ceramic exhibits a negative differential resistance behavior. The impedance spectrum indicates that the sample consists 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 (BIT) and the distribution of every element is uniform. The BGT sample exhibits randomly oriented and plate-like morphology.
149
Authors: Y.H. Sun, Min Chen, W.K. An, A.H. Cai, J. Liu, K.L. Su
Abstract: Tb-doped bismuth titanate (BixTbyTi3O12: BTT) and pure Bi4Ti3O12 (BIT) thin films with random orientation were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well-developed rod-like grains with random orientation. Tb doping into BIT caused a large shift of the Curie temperature (TC) from 675°C to lower temperature. The experimental results indicated that Tb doping into BIT result in a remarkable improvement in dielectric property.
82
Authors: Min Chen, A.H. Cai, X.A. Mei, K.L. Su, Chong Qing Huang, Z.M. Wan, J. Liu
Abstract: Pr6O11-doped bismuth titanate (BixPryTi3O12: BPT) thin films with random oriention 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 BPT films consisted of single phase of a bismuth-layered structure with well-developed rod-like grains. For samples with y=0.06, 0.3, 1.2 and 1.5, ferroelectric hysteresis loops were characterized by large leakage current, whereas for samples with y=0.6 and 0.9, ferroelectric hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BPT Film with y=0.9 were above 35μC/cm2 and 80KV/cm , respectively. After 3×1010 switching cycles, 20% degradation of 2Pr is observed in the film with y=0.9.
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