The macroscopic diffusivity of protons in the α-phase was investigated, at 140 to 910K, by using the pulsed field gradient nuclear magnetic resonance technique. The data for temperatures above 500K were described by:

D (cm2/s) = 1.1 x 10-3 exp[-0.178(eV)/kT]

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

D (cm2/s) = 1.1 x 10-3 exp[-0.187(eV)/kT]

when H/Ta was equal to 0.14.

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