Nuclear magnetic resonance study of hydrogen diffusion in palladium-silver alloys

Abstract

The diffusion of hydrogen in the α′ phase of Pd and PdAg alloys with up to 17% Ag has been studied by proton magnetic resonance. Proton spin-lattice relaxation times, T1, have been measured over the range ~200 K to ~400 K and the diffusion coefficient, D, was also measured directly by the pulsed-field-gradient method in the range ~300 K to ~400 K. The two sets of measurements taken together are consistent with random jumps between nearest neighbour octahedral sites, and are inconsistent with jumps between tetrahedral sites. For a fixed hydrogen concentration, D decreases, d0 increases by a factor of about 2, and the activation energy increases from 0.23 ± 0.01 eVto 0.28 ± 0.02 eV on addition of 17 at.% Ag.