Interfacial defects, such as grain boundary dislocations, play an important role in the creep behavior of alumina. In the present work, interfacial defects were analyzed in detail using a Volterra approach without a reference to a near-coincidence description. Disconnections (boundary steps with dislocation character), in a diffusion-bonded alumina bicrystal with a misorientation close to the rhombohedral twin, were investigated by means of conventional and atomic resolution electron microscopy. The bicrystal contained 2 arrays of parallel disconnections with Burgers vectors that had alternating equal and opposite twist components, so that there was no long-range stress field. This configuration was explained in terms of the stability of various grain boundary disconnection arrangements. The complex core structure of the defects was revealed by high-resolution electron microscopy using exit wave reconstruction. It was shown that the defects were dissociated into 2 partials that delimited grain boundary segments with alternating structure.

Disconnection Arrays in a Rhombohedral Twin in α-Alumina. S.Lartigue-Korinek, S.Hagege, C.Kisielowski, A.Serra: Philosophical Magazine, 2006, 88[10], 1569-79