Hydrothermal synthesis and formation mechanism of tetragonal barium titanate in a highly concentrated alkaline solution

Abstract Tetragonal cube-shaped barium titanate (BaTiO 3 ) was produced by the hydrothermal treatment of a peroxo-hydroxide precursor, a single-source amorphous barium titanate precursor, in a highly concentrated sodium hydroxide solution. Phase pure barium titanate with cube-shaped morphology and particle-sizes in the 0.2–0.5 µm range were formed at temperatures above 80 °C. Also, the cube-shaped morphology of the BaTiO 3 product was preceded by spherical- and plate-like morphologies with, respectively, a Ti-excess and Ba-excess. Coinciding with these morphological observations, changes in the reaction product were also observed. The formation of crystalline BaTiO 3 proceeded alongside secondary BaTi 2 O 5 and Ba 2 TiO 4 phases. These secondary phases disappeared as the reaction time was increased leaving only BaTiO 3 as the sole reaction product. Kinetic analysis of the formation of hydrothermal BaTiO 3 crystallization by the Johnson-Mehl-Avrami method showed that BaTiO 3 crystallization is a homogeneous dissolution-precipitation reaction. The mechanism is governed by nucleation and growth in the beginning of the reaction and dissolution-precipitation dominating throughout the hydrothermal reaction process.