TEM observation of a reactive template for textured Bi0.5(Na0.87K0.13)0.5TiO₃polycrystals

Textured Bi0.5(Na, K)0.5TiO3 (BNKT) ceramics were prepared with high degrees of a preferred pseudocubic {100} orientation by the reactive templated grain growth (RTGG) method in which aligned Bi4Ti3O12 (BIT) plate-like particles were reacted with the other oxides and carbonates to form BNKT. According to the TEM observation of the specimens heat-treated at 700°C, the in-situ reaction from a layered perovskite to a regular perovskite started at the vicinity of the BIT surface and proceeded with heat-treatment time toward the inner part of the BIT. Throughout the observation, the difference between each annealing stage was remarkable when compared with those between each part of the same specimen. The in-situ reaction in this material was topotactic rather than hetero-epitaxial.