The identification of thin amorphous films at grain-boundaries in Al<inf>2</inf>O<inf>3</inf>

The presence of amorphous grain-boundary phases in ceramic materials can significantly influence their properties. Such grain-boundary films can be identified by the dark-field diffuse scattering technique, the Fresnel fringe technique, and analytical electron microscopy (energy-dispersive spectroscopy). However, spectrum artefacts can present major problems for the use of such techniques. Specifically, grain-boundary grooving, surface damage of the specimen and silicon contamination are shown experimentally to arise from ion-milling during the preparation of TEM specimens. It is experimentally shown that, with the above techniques, these artefacts can cause grain-boundaries in commercial alumina specimens to appear to contain glassy phases. The ambiguity in interpreting the results from the use of each of these techniques is discussed in detail. © 1986 Chapman and Hall Ltd.