Ryuta Mitsui

Enhanced piezoelectric properties of (Ba0.3Bi0.7)(Mg0.05Fe0.6Ti0.35)O3 piezoelectric ceramics with high Curie temperature

(Ba0.3Bi0.7)(Mg0.05Fe0.6Ti0.35)O3 ceramics were either doped with vanadium or sintered in calcined powder with the same composition. Compared to an undoped ceramic sintered without the calcined powder, both ceramics showed reduced leakage current densities (lower than 1 × 10-7 A/cm2) and absence of dielectric relaxation behaviors observed in frequency- and temperature-dependent dielectric measurements. The Curie temperatures of both samples were higher than 460°C. The maximum field-induced strain over the applied field, Smax/Emax, of 366 pm/V of the undoped ceramic sintered without the calcined powder increased to 455 and 799 pm/V for the V-doped ceramics and the ceramics sintered with the calcined powder, respectively. The increase was related to a reduced concentration of bismuth vacancy–oxygen vacancy defect dipoles.

Microstructure and Piezoelectric Properties of BaTiO3-Bi(Mg1/2Ti1/2)O3-BiFeO3 Ceramics

Barium titanate (BaTiO3, BT)-bismuth magnesium titanate (Bi (Mg1/2Ti1/2)O3, BMT)-bismuth ferrite (BiFeO3, BF) solid solution ceramics were prepared using a conventional solidstate synthesis, and their piezoelectric properties and microstructure were investigated. Strain electric field curves of the 0.3BT-0.1BMT-0.6BF ceramics with a single perovskite phase were ferroelectric butterfly-like curves. A strain maximum / electric field maximum (Smax/Emax) was 330 pm/V. Transmission electron microscopy revealed ferroelectric-like domain structure in the 0.3BT-0.1BMT-0.6BF ceramics.

Chemical Composition of Dielectric and Piezoelectric Properties for BaTiO3-Bi (Mg1/2Ti1/2)O3-BiFeO3 System Ceramics

1-x-y)BaTiO3-xBi (Mg1/2Ti1/2)O3-yBiFeO3 ceramics were prepared by a conventional solidstate synthesis, and crystal structure and electric properties were investigated. Synchrotron X-ray diffraction pattern revealed that a single perovskite phase was obtained for samples at x=0.05-0.15, y=0.46.5-73.5. Splitting of the (111) peak was observed when (x, y) = (0.050, 0.685) and (0.050, 0.735) indicating that crystal structure of samples changed from a pseudo-cubic phase to a rhombohedral phase with increasing BF. As the BF content increased, the Curie temperature increased. The largest maximum strain (Smax) over the applied maximum electric field (Emax) value (Smax / Emax) of 300 pm/V was observed for 0.365BT-0.050BMT-0.585BF at 25 °C and 1Hz with the Curie temperature of 390 °C.

Piezoelectric enhancement of relaxor-based lead-free piezoelectric ceramics by nanodomain engineering

0.3BaTiO₃-0.1Bi(Mg_1/2Ti_1/2)O₃-0.6BiFeO₃ ceramics were either doped with vanadium or sintered in calcined powder with the same composition. Compared to an undoped ceramic sintered without the calcined powder, both ceramics showed reduced leakage current densities (lower than 1 × 10^-7 A/cm²) and absence of dielectric relaxation behaviors observed in frequency-and temperature-dependent dielectric measurements. The Curie temperatures of both samples were higher than 460 °C. The maximum field-induced strain over the applied field, S_max/E_max, of 366 pm/V of the undoped ceramic sintered without the calcined powder increased to 455 and 799 pm/V for the V-doped sample and the sample sintered with the calcined powder, respectively. The increase was related to a reduced concentration of bismuth vacancy - oxygen vacancy defect dipoles.