Papers by Author: A.H. Cai

Abstract: Dy₂O₃-doped bismuth titanate (Bi_4-xDy_xTi₃O₁₂: 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 (P_r) and coercive field (E_c) 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 P_r is observed in the film.

Abstract: The Al-40Si alloy modified by 0.5 wt% Sr addition was heat treated using L₉(3⁴) orthogonal test. The mechanical properties were measured. The microstructures were analyzed using optical microscope. After heat treatment, the extension percentage increases more than twice. The eutectic matrix and primary Si phase are both refined. The primary Si phase is refined and homogeneously distributes in the matrix with the solution temperature and time increasing. However, the primary Si phase agglomerates each other with further increasing of the solution temperature and time. According to the microstructure, the optimal solution temperature and time are 500 °C and 14 hours, respectively. In addition, the optimal values for the hardness, tensile strength, and extension percentage are 35.4 HRC, 82.2 MPa, and 2.05 %, respectively.

Abstract: 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  1010 switching cycles, 20% degradation of Pr is observed in the film.

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.

Abstract: 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.

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.

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.

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.

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.

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.