Dislocation loops in non-stoichiometric and stoichiometric (Ba,Ca)TiO3 and in stoichiometric BaTiO3, sintered in a reducing atmosphere, were characterized by means of conventional transmission electron microscopy under 2-beam conditions and high-resolution transmission electron microscopic atomic structure analysis. The loops lay mainly on {100} planes, with Burgers vectors of <100>-type. The dynamic behavior of the loops during electron-beam irradiation could be classified into 2 different types. In A-site excess (Ba,Ca)TiO3, the dislocation-loop contrast faded completely. In BaTiO3, and B-site excess (Ba,Ca)TiO3, a fine-line contrast remained. Dislocation loops with Burgers vectors of ½<100>-type, and a resultant crystallographic shear structure with a displacement vector of ½<110>-type after electron-beam irradiation, were suggested to explain residual line images. The disappearance of these line images in A-site excess (Ba,Ca)TiO3 strongly suggested the existence of preferential Ca-ion site occupancy of the crystallographic shear structure.

Dislocation Loop Formation in Non-Stoichiometric (Ba,Ca)TiO3 and BaTiO3 Ceramics. T.Suzuki, M.Ueno, Y.Nishi, M.Fujimoto: Journal of the American Ceramic Society, 2001, 84[1], 200-6