Necessary conditions for the formation of {111} twins in barium titanate

Abstract

The experimental conditions for {111} twin formation in BaTiO(3) mere investigated, When BaTiO(3) compacts without excess TiO(2) were sintered either in an oxidizing atmosphere lair) 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 eseess-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 A2/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.