The diffusive behavior of Cu in 6N-purity material was studied at 218 to 530C. The results could be described by:

D (cm2/s) = 8.0 x 10-4 exp[-5.6(kcal/mol)/RT]

C.T.Candland, D.L.Decker, H.B.Vanfleet: Physical Review B, 1972, 5, 2085-94