Serial sectioning methods were used to study Ca self-diffusion in single crystals which contained up to 75ppm of cation impurities (table 158). The data for 987 to 1246C could be described by:

D (cm2/s) = 5.35 x 103 exp[-4.15(eV)/kT]

By analyzing the results on the basis of a Ca-ion vacancy diffusion mechanism, the migration enthalpy was estimated to be 1.75eV. The order of magnitude of the pre-exponential factor could be explained on the basis of lattice-strain entropy effects. Self-Diffusion of Ca in Single-Crystal CaF2. M.F.Berard: Journal of the American Ceramic Society, 1971, 54[3], 144-6