Chemical diffusion coefficients were determined at 400 to 600C by using electrochemical methods. The results could be described by:

D (cm2/s) = 1.55 x 10-1 exp[-28.4(kcal/mol)/RT]

C.J.Wen, W.Weppner, B.A.Boukamp, R.A.Huggins: Metallurgical Transactions B, 1980, 11[3], 131-7