Point defects in ionic materials have been briefly reviewed. The main
types of intrinsic defects, together with some representative examples
of impurity related defects are described. Several mechanisms of cent
er production, destruction and transformation are discussed. The main
spectroscopic techniques, such as optical absorption, photo- and therm
o-luminescence and magnetic resonances, used in the study of these def
ects and the results obtained with these techniques in some simple cas
es are also presented. Copyright (C) 1996 Elsevier Science Ltd