Formation of (111) Twins in BaTiO3 Ceramics

(111) twins are found frequently in the microstructure of BaTiO₃ ceramics prepared by the mixed-oxide technique. The processing steps by which the (111) twins are formed are in question. A BaCO₃-TiO₂ powder mixture is milled and then Calcined at 1100°C for 2 h, where BaTiO₃ is formed by the release of CO₂. After the powder is calcined, it is analyzed by TEM. Image and diffraction pattern data are combined to prove the presence of (111) twins in powder particles; the formation of (111) twins occurred frequently during calcination. The formation mechanism of such twins and their role during anomalous grain growth are discussed.