Hydrothermal Preparation and Characterization of Ultra-Fine BaTiO3 Powders from Amorphous Peroxo-Hydroxide Precursor

A peroxo complex was prepared by adding hydrogen peroxide to an aqueous solution containing barium nitrate and titanium tetrachloride, and the complex precipitated by addition of ammonia. The precipitate was subjected to hydrothermal treatment at temperatures of 90-150 C for various time periods. The maximum pressure at 150 C was 4.3 MPa. Phase-pure barium titanate powders with a cubic perovskite structure were obtained at temperatures as low as 110 C, at pH 10-12. The unit cell volume decreased with increasing temperature. The particles were spherical, those prepared at 130 C having a diameter of < 30 nm. Compacts sintered at 1200 C for 1 h achieved a density of 97% of theoretical, and a relatively high dielectric constant of 3500. 17 refs.