Molecular beam epitaxial methods were used to grow high-purity material, with buried tracer layers, for diffusion measurements. The diffusion which was detected on both sub-lattices was compared with predictions. In the case of the anion sub-lattice, the rates were slightly higher than theoretically predicted values which were based only upon Schottky pairs. The results provided substantial support for the development of theories which took account of the energy and entropy of the non-linear dielectric relaxation fields near to charged defects in ionic crystals.

M.H.Yang, C.P.Flynn: Physical Review Letters, 1994, 73[13], 1809-12