The application of electron diffraction to the study of surfaces and interfaces in ceramic materials

In this work, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) have been used to study the effects of crystallography on interface mobility, and to study the resultant crystallography subsequent to the movement of an interface. The interfaces studied, are those that result from solid-state reactions, crystal growth, and grain growth in the presence of a liquid phase. The common characteristic of these different types of interfaces is that the crystallography of the material bounding the interface has a direct influence on the mobility of the interface. For example, in solid-state reactions the kinetics of the reaction and the diffusion of the material to the interface are dependent on the crystallography of the materials involved in the reaction. In this work, the reaction between two materials has been studied by EBSD, and the rate of reaction, related to the crystallography of the reactants as well as the reaction product layer. The interface mobility, which occurs during the grain growth of liquid-phase sintering, is influenced by the crystallography of the surfaces bounding the interface as well as those that may be adjacent to the interface. EBSD has been used to determine the orientation of the grains bordering the interface and SEM imaging to correlate migration rate to the grain orientation. The interfaces that are most significant during crystal growth often include only one surface, that of the growth front. The growth rate of a material is dependent on the ability of adsorbed atoms to find a permanent site. The crystallography of a material, the orientation of the surface and the crystallographic nature of the defects present, dictate the number of potential stable sites for adsorbed atoms to find permanence. As growth starts, the crystallography of the substrate surface determines the orientation of the new material growth. Electron diffraction in the TEM has been used to identify and determine the nature of defects and their relationship to the crystallography of the grown material. Diffraction in the TEM has also been used to determine the structure of a thin film and the orientation relationship formed with the substrate.