BaTiO3 powders were synthesized by a hydrothermal process via a co-precipitation route. BaTi-peroxo-hydroxide coprecipitate was formed when a BaCl2, TiOCl2 and H2O2 aqueous solution was added to an ammonium solution and the coprecipitate was used as the precursor for a hydrothermal synthesis process. It was found that phase-pure BaTiO3 powders were formed under mild hydrothermal conditions; over a temperature range of 110-130oC, in the pH range of 10-12 and under a pressure below 1.8 MPa. The crystalline (perovskite) BaTiO3 powders were synthesized from the amorphous precipitate almost immediately without a dissolution process. An ultrafine powder of around 15 nm size was obtained and its BET surface area was as high as 70 m2/g. Using these reactive fine powders, a fairy high density of 97% of theoretical and a high dielectric constant (εr) of 4000 were achieved for the ceramics sintered at a temperature as low as 1200oC.

Keywords: hydrothermal synthesis, co-precipitation, barium titanate, perovskite, powder preparation