Key Engineering Materials Vol. 633

Abstract: Pr₂O₃-doped bismuth titanate (Bi_4-xPr_xTi₃O₁₂: 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 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 ( P_r ) and coercive field (E_c) of the BPT Film with x=0.75 were above 30μC/cm² and 75KV/cm , respectively.

Abstract: The ferroelectricity of Bi_3.25Tm_0.75Ti_2.97V_0.03O₁₂ (BTTV) ceramic prepared at 1200°C by a conventional ceramic technique was investigated. The ceramic possess random-oriented polycrystalline structure. The remanent polarization (P_r) and coercive field (E_c) of the BTTV ceramics are 25 μC/cm² and 70kV/cm, respectively. The P_r value of the BTTV ceramics up to 25 μC/cm² is larger than that of the BTT ceramics. Therefore, co-sustitution of Tm and V in Bi₄Ti₃O₁₂ (BIT) ceramics is effective for the improvement of the ferroelectricity of Bi₄Ti₃O₁₂ ceramics.

Abstract: Dy-doped Bi₄Ti₃O₁₂ thin films were fabricated on Pt/Ti/SiO₂/Si substrates by pulsed laser deposition technique, and the structures and electrical properties of the films were investigated. XRD results indicated that all of Bi_4-xDy_xTi₃O₁₂ 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 Bi_4-xDy_xTi₃O₁₂ Film with x=0.75 were 25μC/cm² and 85KV/cm , respectively.

Abstract: The electrical properties of Pr₂O₃-doped bismuth titanate,Bi_4-xPr_xTi₃O₁₂ (BPT) ceramics prepared by a conventional electroceramic technique were investigated. XRD analyses revealed Bi-layered perovskite structure in all ceramics. SEM micrographs showed randomly oriented and plate-like morphology. For the ceramics with x=0.25 and 1.0 P-E hysteresis loops were characterized by large leakage current, whereas for the ceramics with x=0.5 and 0.75 P-E hysteresis loops were the saturated and undistorted hysteresis loops. The remanent polarization ( P_r ) and coercive field (E_c) of the BPT ceramic with x=0.75 were above 18μC/cm² and 65KV/cm , respectively.

Abstract: The ferroelectricity of Bi_3.2Tb_0.8Ti₃O₁₂ (BTT) and Bi_3.2Tb_0.8Ti_2.97V_0.03O₁₂ (BTTV) ceramics prepared at 1100°C by a conventional ceramic technique was investigated. These ceramics possess random-oriented polycrystalline structure. The remanent polarization (P_r) and coercive field (E_c) of the BTT ceramics are 16 μC/cm² and 75kV/cm, respectively. Furthermore, V substitution improves the P_r value of the BTT ceramics up to 26 μC/cm², which is much larger than that of the BTT ceramics. Therefore, co-sustitution of Tb and V in Bi₄Ti₃O₁₂ (BIT) ceramic is effective for the improvement of its ferroelectricity.

Abstract: 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 Bi_4-xLa_xTi₃O₁₂ (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 ( P_r ) and coercive field ( E_c ) 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.

Abstract: The ferroelectricity of Bi_3.25Sc_0.75Ti₃O₁₂ (BST), and Bi_3.25Sc_0.75Ti_2.97V_0.03O₁₂ (BSTV) ceramics prepared at 1100°C by a conventional ceramic technique was investigated. These ceramics possess random-oriented polycrystalline structure. The remanent polarization (P_r) and coercive field (E_c) of the BST ceramics are 18 μC/cm² and 70kV/cm, respectively. Furthermore, V substitution improves the P_r 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.

Abstract: CrNx coatings were deposited by high power pulse magnetron sputtering in a closed field unbalanced system. The influence of pulse width on microstructure and mechanical properties of CrNx coatings was examined. Morphologies different from those fabricated by traditional magnetron sputtering were obtained, phase structures were also changed in the process. The coatings hardness were always improved in the increasing pulse length, while the best adhension of CrNx coatings about 25N was get when pulse length was 60us.

Abstract: Ceramic coatings were fabricated on pure magnesium in silicate electrolyte system by ultrasonic micro-arc oxidation (UMAO) process, and then silica sol (CSG) and HF-CSG treatment were carried out on micro-arc oxidation coatings. The corrosion potential (E_corr) and corrosion current density (I_corr) of the compound coatings were analyzed by electrochemical corrosion workstation. The corrosive morphology of the coatings was observed by scanning electron microscopy (SEM). Results showed that the E_corr of the coating with CSG and HF-CSG treatment increased by 55 mV and 69 mV respectively in comparison with that of single UMAO coating, and its I_corr reduced an order of magnitude, which had enhanced the corrosion resistance.

Abstract: Yttria doped ceria display higher ionic conductivity and stabilized phase which possess more advantage for solid oxide fuel cells. By using molecular dynamics simulation, the lattice parameter and oxygen conductivity of Ce_1-xY_xO_2-x/2 (x = 0 - 0.65) at 1273 k have been investigated. Lattice parameters and ionic conductivity both increase with yttria doping while x < 0.15 but over doping of yttria lead to a decreasing trend on them. It is suggested that the closing distance of cation-anion is responsible for this decreasing. The coordination numbers of cations were also analyzed. The results showed that the vacancies prefer to locate near Y ions and vacancy ordering is independent with vacancy content.