C.Q. Huang

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.

Ferroelectric and Electrical Behavior of Bi4-xNdxTi3O12 Thin Films

Nd2O3-doped bismuth titanate (Bi4-xNdxTi3O12: BNT) 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 BNT 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 BNT Film with x=0.8 were 25μC/cm2 and 55KV/cm , respectively. After 3×1010 switching cycles, 15% degradation of Pr is observed in the film.

Ferroelectric Property and Microstructures of La-Doped Bi4Ti3O12 Thin Films

La-doped bismuth titanate (Bi4-xLaxTi3O12: BLT) 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. 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-V hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( Pr ) and coercive field (Ec) of the BLT ceramic with x=0.75 were above 20μC/cm2 and 85KV/cm , respectively.

Dielectric and Ferroelectric Properties of Er2O3-Doped Bi4Ti3O12 Thin Films

Er2O3-doped bismuth titanate (Bi4-xErxTi3O12, BET) 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. Er-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 Er doping into BIT also result in a remarkable improvement in ferroelectric property. The Pr and the Ec values of the BET film with x=0.75 were 21 μC/cm2 and 80 kV/cm, respectively.

Electrical Characteristics and Microstructures of Bi2.9Pr0.9Ti3O12 and Bi2.9Pr0.92Ti2.97V0.03O12 Thin Films

Bi2.9Pr0.9Ti3O12(BPT) and Bi2.9Pr0.9Ti2.97V0.03O12(BPTV) 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. The experimental results indicated that Pr doping into Bi4Ti3O12 (BIT) result in a remarkable improvement in ferroelectric property. The remanent polarization (Pr) and coercive field (Ec) of the BPT film were 28 μC/cm2 and 80 kV/cm, respectively. Furthermore, V substitution improves the Pr value of the BTVT film up to 43 μC/cm2, which is much larger than that of the BPT film.

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.