Diffusion through a membrane was studied at temperatures of up to 600C. It was found that the results could be described by:

D (cm2/s) = 0.18 exp[-14.8(kcal/mol)/RT]

M.Braun, B.Emmoth, F.Waelbroeck, P.Wienhold: Journal of Nuclear Materials, 1980, 93-94, 861-5