X.A. Mei

Ferroelectric Properties of Bismuth Titanate Ceramics by Sm3+/V5+ Substitution

The ferroelectricity of Bi3.25Sm0.75Ti3O12 (BST), and Bi3.25Sm0.75Ti2.97V0.03O12 (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 16 µC/cm2 and 64kV/cm, respectively. Furthermore, V substitution improves the Pr value of the BST ceramics up to 25 μC/cm2, which is much larger than that of the BST ceramics. Therefore, co-sustitution of Sm and V in is effective for the improvement of the ferroelectricity of Bi4Ti3O12 ceramic.

Electrical Characteristics and Microstructures of Eu2O3-Doped Bi4Ti3O12 Ceramics

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.

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.

Electrical characteristics and microstructures of Pr6O11-doped Bi4Ti3O12 thin films

Abstract Pr 6 O 11 -doped bismuth titanate (Bi x Pr y Ti 3 O 12 , BPT) thin films with random orientation were fabricated on Pt/Ti/SiO 2 /Si substrates by rf magnetron sputtering technique, and the structures and ferroelectric properties of the films were investigated. XRD studies indicate that all of BPT films consist 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, I — E characteristics exhibit negative differential resistance behaviors and their ferroelectric hysteresis loops are characterized by large leakage current. Whereas for samples with y =0.6 and 0.9, I — E characteristics are of simple ohmic behaviors and their ferroelectric hysteresis loops are saturated and undistorted. The remanent polarization ( P r ) and coercive field ( E c ) of the BPT Film with y =0.9 are above 35 μC/cm 2 and 80 kV/cm, respectively.

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.

Dielectric and Ferroelectric Properties of Bi2.9Pr0.9Ti2.97V0.03O12

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.

Impedance Spectra and Ferroelectric Properties of Bismuth Titanate Ceramics by Nd3+/V5+ Substitution

The ferroelectricity of Bi3.25Nd0.75Ti3O12 (BNT), and Bi3.25Nd0.75Ti2.97V0.03O12 (BNTV) 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 BNT ceramics are 16 µC/cm2 and 65kV/cm, respectively. Furthermore, V substitution improves the Pr value of the BNTV ceramics up to 23 μC/cm2, which is much larger than that of the BNT ceramics. Therefore, co-sustitution of Nd and V in Bi4Ti3O12 ceramic is effective for the improvement of its ferroelectricity.

Electrical Characteristics and Impedance Spectra of Gd2O3-Doped Bi4Ti3O12 Ceramics

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.

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 Tb4O7-Doped Bi4Ti3O12 Thin Films

Tb4O7-doped bismuth titanate (BixTbyTi3O12 BTT) 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 BTT films with well-developed rod-like grains consist of single phase of a bismuth-layered structure without preferred orientation. The experimental results indicate that Tb doping into Bi4Ti3O12 results in a remarkable improvement in ferroelectric properties. The remanent polarization (Pr) and coercive field (Ec) of the BTT film with y=0.6 were 22 μC/cm2 and 85 kV/cm, respectively.