Alumina bicrystals with a [1¯1▪0] 2° tilt grain boundary, including a slight twist component, were fabricated by using diffusion bonding to study the change in structure due to the presence of the twist component. The resultant grain boundary structure was investigated by means of high-resolution transmission electron microscopy and was compared with that of the pure 2° tilt grain boundary. It was confirmed that the pure 2° tilt boundary was composed of basal dislocations which were similar to those produced by basal slip in alumina single crystals. On the other hand, in the case of boundaries with a slight twist component an unique dislocation structure, composed of partial dislocations in groups of 5, was found in addition to the basal dislocations. The partial dislocations in groups of 5 had a total edge component of 1/6[11▪0] x 5, which compensated the given tilt angle as did the basal dislocations. In addition, they had a total screw component of ½[1¯1▪0]; formed to compensate the twist angle of about 0.16°. The structure of the boundary dislocations therefore changed noticeably due to the presence of the very low twist angle.

Multiple Dissociation of Grain Boundary Dislocations in Alumina Ceramics. A.Nakamura, K.Matsunaga, T.Yamamoto, Y.Ikuhara: Philosophical Magazine, 2006, 86[29-31], 4657-66