Papers by Author: Shigeki Sato

Abstract: Barium titanate (BaTiO3) particles with average size of smaller than 100 nm were synthesized by a hydrothermal process at 100°C to 300°C. The c- to a-axis ratios of the particles increased as the synthesis temperature increased. Disk capacitors were fabricated with as-synthesized particles and some additives to obtain X7R capacitors. The temperature coefficient of capacitance with particles synthesized at 100°C was much larger than that for 300°C, indicating that the former had uniform composition in the grain while the latter had a core-shell structure. This data show that barium titanate particles hydrothermally synthesized at high temperature are useful when creating the X7R capacitors with small grain size.

Abstract: Barium titanate (BaTiO3) nano-particles with high crystalinity were synthesized by hydrothermal process using Ba(OH)2·8H2O and TiO2 as source materials. The average size of the synthesized BaTiO3 particles decreased as the TiO2 particle size decreased. The amount of hydroxide ions incorporated into the perovskite lattice decreased as the BaTiO3 particle size increased and then became constant above 50 nm. Moreover, the ratio of the c- to a-axis length increased when the BaTiO3 particle size was above 50 nm. Sintered ceramics with a grain size smaller than 100 nm were obtained by using highly crystallized hydrothermal BaTiO3 particles.