Radioactive tracer methods were used to study diffusion in polycrystalline samples. It was found that the results between 1000 and 1200C could be described by:

D(cm2/s) = 5 x 10-5exp[-0.87(eV)/kT]

V.P.Prutkin, A.S.Lyutovich, M.J.Kardzhaubaev: Krist. Tonkikh Plenok, 1970, 139-45