Hydrothennal synthesis of high-purity BaTiO3 powders:: control of powder phase and size, sintering density, and dielectric properties

High-purity BaTiO3 fine powders have been synthesized hydrothermally from BaCl2 and TiCl4 under moderate conditions, and the tetragonal content and particle size of as-prepared powders have been characterized quantificationally. Eighty-nanometer and 40% tetragonal content BaTiO3 powders can be obtained by adjusting the hydrothermal temperature and the initial concentration of TiCl4 to a value of 240 degreesC and 1.00 mol/l. At a lower hydrothermal temperature, 80-nm cubic BaTiO3 powders result; and at a lower initial concentration of TiCl4, 150- and 500-nm BaTiO3 powders with 40% 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% tetragonal content has the highest sintering density (5.83 g/cm(3) and 96.5% of the theoretical density) and the highest dielectric constant (6200) and the lowest dielectric loss. (C) 2003 Elsevier B.V. All rights reserved.