The diffusion of 68Ge was studied in 5N-purity material at 975 to 1400C. The diffusion coefficient could be described by:

D (cm2/s) = 4.6 x 10-4 exp[-6.12(kcal/mol)/RT]

Y.P.Gupta, H.S.Wang: Transactions of the Metallurgical Society of AIME, 1969, 245[4], 619-22