A pulsed field gradient nuclear magnetic resonance spin-echo technique was used to measure diffusivities. The activation energy increased with increasing H concentration, whereas the pre-exponential factor was not greatly concentration-dependent (table 94). The results were not consistent with the random occupation of tetrahedral sites, and it was suggested that repulsive interactions existed between H atoms on nearest-neighbor sites.

Diffusion and NMR Spin Lattice Relaxation of 1H in α′ TaHx and NbHx. P.E.Mauger, W.D.Williams, R.M.Cotts: Journal of Physics and Chemistry of Solids, 1981, 42[9], 821-6

Table 95

Isotope Effect for H and D Diffusion and Permeation in Nb