Electron Diffraction and Microscopy Studies of the Structure of Grain Boundaries in Al₂O₃

Electron diffraction and weak‐beam imaging techniques were used to examine the structure and thickness of grain boundaries in polycrystalline Al₂O₃. Extra diffraction spots from boundaries inclined to the foil surface were detected and related to the periodic structure of the boundary. Relrods from edge‐on boundaries were detected and used to estimate the thickness of the boundary region, i.e. the depth that the displacement field of the boundary penetrates into the two crystals adjacent to the interface.