Synthesis of Crystal-Axis-Oriented BaTiO3 and Anatase Platelike Particles by a Hydrothermal Soft Chemical Process

BaTiO3 and anatase with platelike particle morphology were prepared by using a hydrothermal soft chemical process. A layered titanate of K0.8Ti1.73Li0.27O4 with a lepidocrocite-like layered structure, which has a platelike particle morphology, was used as a precursor. In the first step, the layered titanate was treated with an acid solution to obtain an H+-form layered titanate H1.07Ti1.73O4·nH2O with a lepidocrocite-like layered structure. In the second step, the H+-form layered titanate was treated in a Ba(OH)2 solution or distilled water under mild hydrothermal conditions to transform the layered titanate to BaTiO3 or anatase. The transformation reactions were investigated by XRD and SEM analyses. There are two simultaneous mechanisms in the formation of BaTiO3 under the hydrothermal conditions. One is an in situ topotactic transformation reaction in the crystal bulk of the layered titanate, and another is a dissolution−deposition reaction on the surface of the particles. In the formation of BaTiO3, the in situ topotactic transformation reaction is predominant in the solution of low Ba(OH)2 concentration, while, in the formation of anatase, most of the reaction progressed by the in situ topotactic transformation mechanism. The platelike particles of BaTiO3 and anatase, which were prepared by this method, showed a high degree of crystal-axis orientation.