By using a steady-state flow method, the diffusivities at 250 to 400C were found to be described by:

D (cm2/s) = 1.4 x 10-3 exp[-4.9(kJ/mol)/RT]

V.A.Kurakin, A.A.Kurdyumov, V.N.Lyasnikov, M.I.Potapov: Fizika Tverdogo Tela, 1979, 21[4], 1060-3