XCII. Impurity diffusion in polar crystals

Abstract

A theoretical discussion of the diffusion of divalent impurities in polar crystals of the NaCl-type is given with the aid of the Stasiw-Teltow association model. It is shown how accurate measurements of the impurity diffusion coefficient can yield fundamental information about the existence and concentration of impurity-vacancy pairs (‘complexes’) in a simple and direct manner. Such measurements would therefore provide a valuable addition to the studies of ionic crystals already made of their ionic conductivity, dielectric loss, etc. The main restriction of the present theory is that the impurity-vacancy complexes should have a mean lifetime which is long compared with the mean jump times which govern their changes of position and orientation.