The self-diffusion of 95Nb in single crystals of NbC0.868, NbC0.834 and NbC0.766 was studied at 2370 to 2660K. The diffusion coefficients were composition independent and could be described by:

D(cm2/s) = 4.54 exp[-140.0(kcal/mol)/RT]

B.B.Yu, R.F.Davis: Journal of Physics and Chemistry of Solids, 1981, 42[2], 83-7