Formation mechanism of barium titanate nanocrystals under hydrothermal conditions

Growth units and the crystallization habit of BaTiO₃ nanocrystals have been investigated. It has been proposed that the growth units of BaTiO₃ were surface hydroxylated Ti(OH)₆²⁻ octahedra. The relationship between crystal morphology and the variation of the current intensity in the solution has been obtained through the measurement of the OH⁻ in the solution and the hydrothermal experiment with superimposed direct electric field. Based on the computation of the stability energy of the growth units, the relationship between the crystallized morphology of crystallites and the most favorable growth units under different conditions has been derived. It has been found that there is structure similarity between anatase (TiO₂) and BaTiO₃ from the crystal chemistry viewpoint, so they are soluble in each other, which can serve as a reasonable explanation for the abnormal phenomenon of the retention of cubic substable phase at room temperature. Project supported by the National Natural Science Foundation of China.