High-temperature creep in ceramics

Creep in ceramics is discussed as opposed to metals in the light of previous findings. Three aspects of the issue are singled out. They are the phenomenology of the process, that is, the kinetics of deformation (creep curves) and their dependence on temperature and load; the evolution of the process at the microscopic level and the role of some structural characteristics; and elementary deformation events largely determined by the type of chemical bonding and the structure of the unit cell. It is shown that crystalline inorganic dielectrics differ from metals not only in the underlying mechanisms of mass transfer, but also in the action of the mechanical stress gradient: in metals, mass transfer is mainly effected by shear, whereas in ceramics it is controlled by diffusion.