Effect of sintering temperature on the secondary abnormal grain growth of BaTiO3

When BaTiO3 specimens containing a small amount of excess TiO2 were sintered for more than 15 h, some grains grew abnormally to several millimeters in size. This phenomenon may be referred to as the secondary abnormal grain growth (SAGG) because it occurred from a large and uniform grain structure (average grain size: 70 μm) after completion of primary abnormal grain growth. SAGG was observed only at a very narrow temperature range between 1360 and 1370°C, where the solid–liquid interface structure was atomically smooth. Almost all the secondary abnormal grains contained the (111) double twin, which provides the persistent twin-plane re-entrant edge (TPRE). During SAGG, the growth of matrix grains was strongly suppressed and material transfer occurred preferentially to the grains with a (111) double twin.