M. Chen

Negative Resistance Behavior of Ferroelectric Bismuth Titanate Ceramics at Low Field

Ferroelectric Bi4Ti3O12 ceramics are fabricated by conventional solid-state reaction process. The current-voltage characteristic of Bi4Ti3O12 sample exhibits a voltage-controlled negative differential resistance behavior at low field (E≤100V/mm), and an obvious PTC effect appears at around 100°C on the resistance-temperature curve. Based on conducting filament model about electrical transport, instead of Heywang-Jonker model, the experimental results of Bi4Ti3O12 ceramics are suitably explained.

Ferroelectric Properties and Microstructures of Tb2O3-Doped Bismuth Titanate Ceramics

The electrical properties of Tb2O3-doped bismuth titanate,Bi4-xTbxTi3O12 (BTT) ceramics prepared by a conventional electroceramic technique have been investigated. XRD analyses indicted Bi-layered perovskite structure in all samples, and revealed that Bi ions were only substituted near the Ti-O octahedron layers by Tb ions. SEM micrographs show randomly oriented and plate-like morphology. The remanent polarization ( Pr ) and coercive field ( Ec ) of the BTT ceramics with x=0.75 were above 16μC/cm2 and 75KV/cm, respectively. The large value of remanent polarization and low coercive field of Tb-doped bismuth titanate ceramics promote these materials to potential applications.

Electrical Characterization and Microstructures of Ce-Doped Bi4Ti3O12 Thin Films

Tb-doped bismuth titanate (Bi4-xCexTi3O12: BCT) 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. Ce-doping into BIT caused a large shift of the Curie temperature (TC) from 675°C to lower temperature and a improvement in dielectric property. The experimental results indicated that Ce doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BCT film with x = 0.75 were 23 μC/cm2 and 80 kV/cm, respectively.

Ferroelectric Properties and Microstructures of Pr6O11-Doped Bi4Ti3O12 Thin Films

Pr6O11-doped bismuth titanate (BixPryTi3O12 BPT) thin films were fabricated on Pt/Ti/SiO2/Si substrates by rf magnetron sputtering technique, and the microstructures and ferroelectric properties of the films were investigated. Microstructure studies indicate that all of BPT films with well-developed rod-like grains consist of single phase of a bismuth-layered structure without preferred orientation. Pr doping into Bi4Ti3O12 (BIT) causes a large shift of the Curie temperature (TC) of paraelectric-ferroelectric phase transition of BIT from 675°C to lower temperature and improvement in dielectric properties. The experimental results indicate that Pr doping into Bi4Ti3O12 results in a remarkable improvement in ferroelectric properties. The remanent polarization ( Pr ) and coercive field (Ec) of the BPT film with y=0.9 were 35 μC/cm2 and 80 kV/cm, respectively. After 3 uf0b4 1010 switching cycles, 20% degradation of Pr is observed in the film.

Optimization of Compositional and Technological Parameters for Phosphate Graphite Sand

In present work, the compression strength and tensile strength of phosphate graphite sand with compositional and technological parameters (phosphoric acid, Al2O3, drying temperature, and drying time) were experimentally investigated. An L9 (34) orthogonal array was employed to analyze the effect of these four parameters on the compression strength and tensile strength, respectively. In addition, the radial basis function artificial neural network (RBFANN) was used to establish the models for compression strength and tensile strength, respectively. Moreover, the simulation and prediction results by the RBFANN and linear and non-linear regressions are compared. The results are as follows: the optimum scheme for phosphate graphite sand designed by us is phosphoric acid 24%, Al2O3 30%, drying temperature 400xa0°C, and drying time 60xa0min. The ascending sequence of the effect of four factors on both compression strength and tensile strength of phosphate graphite sand is drying time, drying temperature, Al2O3, and phosphoric acid. In addition, the prediction and simulation results show that RBFANN outperforms Taguchi approach for modeling.

Effect of Sc2O3/V2O5 Substitution on the Ferroelectric Properties of Bi4Ti3O12 Ceramics

The ferroelectricity of Bi3.25Sc0.75Ti3O12 (BST), and Bi3.25Sc0.75Ti2.97V0.03O12 (BSTV) ceramics prepared at 1100°C by a conventional ceramic technique was investigated. These ceramics possess random-oriented polycrystalline structure. The remanent polarization (Pr) and coercive field (Ec) of the BST ceramics are 18 μC/cm2 and 70kV/cm, respectively. Furthermore, V substitution improves the Pr value of the BST ceramics up to 26 μC/cm2. Therefore, co-sustitution of Sc and V in Bi4Ti3O12 (BIT) ceramic is effective for the improvement of its ferroelectricity.

The Effect of La Substitution on the Ferroelectric Properties of Bi4Ti3O12 Ceramics

The effect of La substitution on the ferroelectric properties Bi4Ti3O12 ceramics prepared by a conventional electroceramic technique has been investigated. XRD analyses revealed Bi-layered perovskite structure in all Bi4-xLaxTi3O12 (BLT) ceramics samples, and indicted that Bi ions were only substituted near the Ti-O octahedron layers by La ions. SEM micrographs show randomly oriented and plate-like morphology. The remanent polarization ( Pr ) and coercive field ( Ec ) of the BLT ceramic with x=0.8 were above 15μC/cm2 and 85KV/cm, respectively. The large value of remanent polarization and low coercive field of La-doped bismuth titanate ceramics promote these materials to potential applications.

Effect of Gd Substitution on Electrical Characteristics and Microstructures of Bi4Ti3O12 Ceramics

The electrical properties of Gd-doped bismuth titanate Bi4-xGdxTi3O12 (BGT) 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 ceramics with x=0.25 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 ceramics with x=0.5 and 0.75 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 BGT ceramic with x=0.8 were above 16μC/cm2 and 70KV/cm , respectively.

Preparation and Electrical Characteristics of Bi4-xYbxTi3O12 Ceramics

The electrical properties of Yb-doped bismuth titanate,Bi4-xYbxTi3O12 (BYbT) 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=0.25 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=0.5 and 0.75 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 BYbT ceramic with x=0.75 were above 16μC/cm2 and 75KV/cm , respectively.

Electrical Characterization and Microstructures of Bi4-xScxTi3O12 Ceramics Grown by Electroceramic Technique

Sc-doped bismuth titanate (Bi4-xScxTi3O12: BST) and pure Bi4Ti3O12 (BIT) ceramics with random orientation were fabricated by a conventional electroceramic technique. These samples had polycrystalline Bi-layered perovskite structure without preferred orientation, and consisted of well developed plate-like grains with random orientation. Sc-doping into BIT caused a large shift of the Curie temperature ( TC ) from 675 °C to lower temperature and a improvement in dielectric property. The experimental results indicated that Sc doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BST ceramic with x=0.75 were 16 μC/cm2 and 85 kV/cm, respectively.