The H migration characteristics were determined, at 700 to 1400K, by using H pressures which ranged from 0.013 to 4.26Pa. At temperatures greater than 1100K, the H diffusivity could be described by:

D (cm2/s) = 4.4 x 10-4 exp[-3.1(kcal/mol)/RT]

At lower temperatures, the diffusivity decreased below the extrapolated values of this expression. This behavior was attributed to the effect of surface impedence. An isotope effect was detected in the diffusivities of H and D.

R.Sherman, H.K.Birnbaum: Metallurgical Transactions A, 1983, 14[2], 203-10

The best linear fits to the solute diffusion data ([1015] to [1019], [1021] to [1030]) yield:

H: Ln[Do] = 0.55E – 9.4 (R2 = 0.92); N: Ln[Do] = 0.23E – 12.2 (R2 = 0.73);

Nb: Ln[Do] = 0.20E – 19.4 (R2 = 0.94)