Necessary Conditions for the Formation of {111} Twins in Barium Titanate

The experimental conditions for {111} twin formation in BaTiO 3 were investigated. When BaTiO 3 compacts without excess TiO 2 were sintered either in an oxidizing atmosphere (air) or in a reducing atmosphere (95N 2 –5H 2 ), no {111} twins formed within the BaTiO 3 grains and no abnormal grain growth occurred. In contrast, many {111} twins were present within the abnormally grown grains in the excess‐TiO 2 ‐containing BaTiO 3 samples sintered in air, while no twins were observed in the excess‐TiO 2 ‐containing samples sintered in 95N 2 –5H 2 . X‐ray diffraction analysis showed that excess TiO 2 forms a Ba 6 Ti 17 O 40 phase during sintering with the space group A 2/ a in air and a Ba 6 Ti 17 O 40− x phase with the space group C in 95N 2 –5H 2 . It appears therefore that excess TiO 2 and an oxidizing atmosphere are necessary for {111} twin formation in BaTiO 3 . These results may also indicate that the interface structure between BaTiO 3 and Ba 6 Ti 17 O 40 influences the twin formation.