Bicrystals with large interfacial areas and controlled misorientations were prepared by using the solid-phase inter-growth method. The structures of three [00•1] tilt boundaries, with misorientations of less than 1º, 17.8º or 31.5º, were studied by using high-resolution electron microscopy. The low-angle boundary comprised well-separated crystal dislocations, and the atomic structure of the large-angle boundaries could be described in terms of sequences of [00•1] tunnels that were coordinated, 5-fold, 6-fold and 7-fold, by atomic columns. It was found that the 17.8º asymmetrical (¯9 17 ¯9 0) boundary, Σ = 31, was planar and exhibited a relatively long-period repeating structure which was occasionally interrupted by interfacial dislocations. The Burgers vectors and step nature of these defects were investigated by using circuit mapping and were found to be consistent with topological theory. The 31.5º interface was found to be extensively facetted into (¯2 7 ¯5 0) and (1 3 ¯4 0) symmetrical tilt boundaries. Mirror symmetry in the immediate vicinity of the interface was suppressed by local relaxation. An angular deviation, of -0.7º, from the periodic Σ = 13 system was seen to be accommodated by primitive interfacial dislocations. Some of these defects exhibited compact cores; thus introducing minimal disruption into the underlying periodic structure. Others exhibited a more complex reconstruction, leading to a reduction in interfacial area and defect energy.

A.N.Kiselev, F.Sarrazit, E.A.Stepantsov, E.Olsson, T.Claeson, V.I.Bondarenko, R.C.Pond, N.A.Kiselev: Philosophical Magazine A, 1997, 76[3], 633-55