A pulsed-field gradient nuclear magnetic resonance spin echo technique was used to measure the diffusivities in TaHx. It was found that the activation energy increased with increasing H concentration, whereas the pre-exponential factor was not markedly concentration-dependent:

TaH0.12:     D (cm2/s) = 3.1 x 10-4 exp[-0.143(eV)/kT]

TaH0.17:     D (cm2/s) = 4.6 x 10-4 exp[-0.164(eV)/kT]

TaH0.34:     D (cm2/s) = 3.5 x 10-4 exp[-0.162(eV)/kT]

TaH0.38:     D (cm2/s) = 4.1 x 10-4 exp[-0.170(eV)/kT]

TaH0.52:     D (cm2/s) = 4.3 x 10-4 exp[-0.182(eV)/kT]

TaH0.74:     D (cm2/s) = 2.6 x 10-4 exp[-0.170(eV)/kT]

TaH0.77:     D (cm2/s) = 3.3 x 10-4 exp[-0.183(eV)/kT]

The results were not consistent with the random occupation of tetrahedral sites.

P.E.Mauger, W.D.Williams, R.M.Cotts: Journal of the Physics and Chemistry of Solids, 1981, 42[9], 821-6