Hydrothermal synthesis of high-purity BaTiO_3 powders: control of powder phase and size, sintering density, and dielectric properties

摘要

High-purity BaTiO_3 fine powders have been synthesized hydrothermally from BaCl_2 and TiCl_4 under moderate conditions, and the tetragonal content and particle size of as-prepared powders have been characterized quantificationally. Eighty-nanometer and 40 percent tetragonal content BaTiO_3 powders can be obtained by adjusting the hydrothermal temperature and the initial concentration of TiCl_4 to a value of 240 deg C and 1.00 mol/l. At a lower hydrothermal temperature, 80-nm cubic BaTiO_3 powders resu and at a lower initial concentration of TiCl_4, 150- and 500-nm BaTiO_3 powders with 40 percent tetragonal phase content result. Because of the successful preparation of these powders, the effect of powder phase and size on the sintering density and dielectric properties of these powders is more clearly investigated. The effect of tetragonal content on the dielectric constant is much more significant than the effect of the particle size. The powder with 80 nm average size and 40 percent tetragonal content has the highest sintering density (5.83 g/cm~3 and 96.5 percent of the theoretical density) and the highest dielectric constant (6200) and the lowest dielectric loss.