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 usin g a hydrothermal soft chemical process. A layered titanate of K0.8Ti1.73Li0 .27O4 With a lepidocrocite-like layered structure, which has a platelike pa rticle morphology, was used as a precursor. In the first step, the layered titanate was treated with an acid solution to obtain an Hf form layered tit anate H1.07Ti1.73O4. nH(2)O With a lepidocrocite-like layered structure. In the second step, the Hf-form layered titanate was treated in a Ba(OH)(2) s olution or distilled water under mild hydrothermal conditions to transform the layered titanate to BaTiO3 or anatase. The transformation reactions wer e investigated by XRD and SEM analyses. There are two simultaneous mechanis ms in the formation of BaTiOs under the hydrothermal conditions. One is an in situ topotactic transformation reaction in the crystal bulk of the layer ed titanate, and another is a dissolution-deposition reaction on the surfac e of the particles. In the formation of BaTiO3, the in situ topotactic tran sformation reaction is predominant in the solution of low Ba(OH)(2) concent ration, while, in the formation of anatase, most of the reaction progressed by the in situ topotactic transformation mechanism. The platelike particle s of BaTiO3 and anatase, which were prepared by this method, showed a high degree of crystal-axis orientation.