Determining factors of crystalline orientation for Bi0.5Na0.5TiO3-based bulk ceramics textured by reactive-templated grain growth

Texture development of Bi0.5Na0.5TiO3 (BNT)-based ceramics was investigated by the observation of microstructure during the reactive-templated grain growth (RTGG) processing. The important process steps in this method to achieve a high degree of orientation are (1) the formation of a homotemplate from a reactive template by in situ reaction and (2) the growth of the homo-template particle at the expense of matrix particles. The BiT particles convert into single-crystal simple perovskite-type platelike particles via polycrystalline skeleton particles. Partial substitution of potassium for sodium in BNT and the existence of a liquid phase during heat treatment promote the formation of the template from the skeleton particles, for which the development of {100} facets is responsible. Furthermore, the growth of matrix grains, which has an adverse effect on the texture formation, is suppressed by the formation of {100} facets with low surface energy. The relative size of reactive template to matrix grain size also affects the templated grain growth behavior.