Preparation of monodispersed spherical barium titanate particles

Abstract

Spherical barium titanate particles with cubic phase were synthesized by a low-temperature hydrothermal reaction. Firstly, The method of hydrolysis of titanium tetrachloride was used for producing spherical TiO₂ particles (0.45–1.5 μ m) with various concentrations of TiCl₄(0.05–0.2 M) and volume ratios of acetone to water solutions (RH = 0–4). These TiO₂ particles were converted to barium titanate by a hydrothermal conversion in a barium hydroxide solution. The size and morphology of the TiO₂ particles was controlled by the volume ratio of acetone to water (RH ratio) in the mixed solvent. At the RH ratio of 3, the morphology of TiO₂ particles was very uniform and discrete. These TiO₂ particles were in the anatase phase and were converted to the rutile phase when the calcination temperature increased to 700∘C and above. Uniform and spherical barium titanate particles were successfully synthesized from the as-prepared TiO₂ particles by using a hydrothermal reaction in a barium hydroxide solution. The Ba/Ti ratios, reaction temperature, and reaction time did not influence the size and morphology of BaTiO₃ particles, but increased the concentration of unfavorable salts such as Ba(OH)₂ and BaCO₃. The high purity BaTiO₃ particles could be obtained by washing with formic acid to remove the unfavorable salts. The size and morphology of the BaTiO₃ particles remained the same as those of the TiO₂ particles, confirming the in-situ transformation mechanism for the conversion of TiO₂ to BaTiO₃. The as-synthesized particles were cubic phase and transformed to tetragonal phase after calcinations at 1150∘C for 1 h. The mean density of the pellets sintered at 1300∘C for 2 h was 5.86 g/cm³ and accounted for 97.34% of the theoretical density.