Point Defects, Charge, and Diffusion

Abstract

Until now we have only considered the ideal structures of crystals, where each atom or ion is on a regular site in the crystal. Real crystals contain a variety of imperfections or defects. In crystalline ceramics and glasses, the structure and chemistry of the material is determined by the kinetics of defect movement. For example, the kinetics of the glass-to-crystal transformation are slow if the temperature is low (typically <1,000°C) because the transformation occurs by atoms moving—in ceramics, this usually occurs by point defects moving. If point defects move too slowly, the structure with the lowest energy (the equilibrium structure) may never actually be achieved. How fast they move is determined by their structure.