Effect of Twin‐Plane Reentrant Edge on the Coarsening Behavior of Barium Titanate Grains

When BaTiO 3 ceramics were sintered at relatively low temperatures (≤1250°C), the grains with reentrant edges caused by a (111) double twin grew exclusively. As a result, a microstructure with a bimodal grain‐size distribution composed of platelike large grains and fine matrix grains was obtained. In contrast, at the usual sintering temperature between 1250° and 1350°C, grains containing a (111) double twin did not exhibit any growth advantage. In this case, a coarse and uniform microstructure was obtained. When this coarse‐grained specimen was further heat‐treated at 1365°C, the grains possessing a double twin were observed to grow exclusively again. The results were explained in terms of a coarsening process controlled by two‐dimensional nucleation.