X-ray diffraction study of large-angle twist grain boundaries

It is demonstrated that the structure of large angle grain boundaries can be studied using X-ray diffraction techniques. A gold bicrystal specimen containing a large-angle 〈001〉 twist boundary has been examined with CuKα radiation and the presence of extra reflections associated with the 0-lattice and coincidence site lattice (CSL) of the boundary detected. The relative intensities of the 0 and CSL reflections are discussed in terms of the displacement field associated with the twist boundary. In order to obtain an appreciation of the magnitude of the scattering from the boundary, calculated structure factors for small and large angle twist boundaries are compared to the structure factor for single (001) planes of gold atoms. It is then seen that the weakest reflections detectable from the boundary correspond to the scattering from one-seventh of a monolayer of gold atoms, which suggests that the X-ray technique used here may also be applied to study the surface structure of thin films.