Data on Nb diffusion, at temperatures ranging from 1200 to 1500K, were obtained by using electron probe microanalysis. It was found that the temperature dependence of the diffusivity could be described by the relationship:

D (m2/s) =1.04 x 10-6exp[-202.59(kJ/mol)/RT]

It was shown that the diffusivity of Nb was almost an order of magnitude higher than the self-diffusion of Ni. It was concluded that the large difference in the activation energies (78.31kJ/mol) reflected the existence of a rather large impurity-vacancy binding energy.

R.V.Patil, G.B.Kale: Journal of Nuclear Materials, 1996, 230[1], 57-60