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 mum) 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 700degreesC 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 1150degreesC for 1 h. The mean density of the pellets sintered at 1300degreesC for 2 h was 5.86 g/cm(3) and accounted for 97.34% of the theoretical density. (C) 2005 Springer Science + Business Media, Inc.