The mechanism of near-surface isotope diffusion was investigated by using the edge source method. It was found that divalent Co ions diffused more rapidly than trivalent Cr ions in the surface layer of MgO. This was also true of the lattice diffusion. The latter behavior was attributed to the fact that the trivalent ion in a divalent matrix had a larger impurity-vacancy bonding energy than did a divalent ion.

V.S.Stubican: Philosophical Magazine A, 1993, 68[4], 809-18