Preparation of Fine Tetragonal Barium Titanate Powder by a Microwave–Hydrothermal Process

A microwave–hydrothermal (MH) process was performed at 240°C to prepare tetragonal BaTiO 3 from TiCl 4 and Ba(OH) 2 . No alkali hydroxide was used to avoid contaminations. MH BaTiO 3 powder with a c / a ratio of 1.010 and a mean size of 180 nm was synthesized within only 9 h. The MH BaTiO 3 contains a very low concentration of lattice hydroxyl group, associated with a very small lattice strain. The measured density of the MH BaTiO 3 is favorably consistent with the theoretical value, and the Ba/Ti stoichiometry determined is 0.996. The formation of a tetragonal structure in BaTiO 3 and the particle growth were strongly promoted by the MH process. The effects of lattice defects on the stoichiometry and the determination of transition enthalpy were discussed.