Low-index symmetrical tilt grain boundaries in the α-phase were investigated by combining high-resolution transmission electron microscopy and spatially-resolved energy dispersive X-ray analysis. Bicrystals with a well-defined orientation relationship and interface plane were prepared by diffusion bonding under an ultra-high vacuum. It was found that grain boundaries such as the prismatic and rhombohedral twin developed an atomically sharp and clean interface, while higher-index grain boundary planes exhibited a more complex structure and were able to accommodate both Si and Ca at the interface. Asymmetric grain boundary planes which occurred as facets at rhombohedral and prismatic twins also accommodated impurity atoms.

Structure and Chemistry of Symmetrical Tilt Grain Boundaries in α-Al2O3 - Bicrystals with “Clean” Interface. T.Gemming, S.Nufer, W.Kurtz, M.Rühle: Journal of the American Ceramic Society, 2003, 86[4], 581-9