The macroscopic diffusivity of protons in the α-phase was investigated, at temperatures of between 140 and 910K, by using the pulsed field gradient nuclear magnetic resonance technique. The data, at temperatures greater than 500K, could be described by:

D (m2/s) = 1.1 x 10-7 exp[-0.178(eV)/kT]

when H/Ta was equal to 0.04, and by:

D (m2/s) = 1.1 x 10-7 exp[-0.187(eV)/kT]

when H/Ta was equal to 0.14. The concentration dependence of the diffusivity at 670K was determined for H/Ta ratios of between 0.03 and 0.14. The results could be described by:

D (m2/s) = (5.45 x 109)[1 - 1.67(H/Ta)]

In the overlap region (140 to 570K), the agreement with Gorsky-effect data was good.

M.Hampele, R.Messer, A.Seeger: Zeitschrift für Physikalische Chemie, 1989, 164[1], 879-82