Grain boundary structure observed by T.E.M
This paper reports some observations on gold by TEM which imply that the dissociation of a high angle grain boundary into two lower energy boundaries may occur extensively.It is well established that grain boundaries of any desired geometry can be created in gold by the welding together of thin single crystals. The resultant thin bicrystal specimens are ideally suited for immediate examination by TEM and many aspects of grain boundary structure and behaviour in such specimens have been studied or discussed. One particularly useful specimen configuration can be achieved if the bicrystal is annealed until its boundary migrates (lowering its total area) until it is perpendicular to the surface of the thin specimen. This specimen geometry has been used to study, inter alia, the faceting of grain boundaries.During a study of the behaviour of coincidence high angle boundaries (i.e. those special boundaries whose geometry is such that a fraction 1/Σ of the lattice sites in both crystals coincide) it was noticed that the boundary under observation was no longer a single planar defect.