High-resolution transmission electron microscopy revealed changes that were due to Ca segregation in the structure of (¯11•4) twin boundaries in -phase material. Doped and undoped twins were prepared by means of the ultra-high vacuum diffusion bonding of 2 high-purity monocrystals. Two distinct boundary configurations, with mirror and glide mirror symmetry, were found in Ca-doped bi-crystals. Only the mirror-related configuration could be identified in the undoped boundary. In order to deduce the structure of the grain boundary, simulated images of 4 super-cells with various Ca contents were compared with experimental high-resolution transmission electron micrographs.

T.Höche, M.Rühle: Journal of the American Ceramic Society, 1996, 79[7], 1961-6