The dynamics of H in the α-phase of Pd1-xAgxHy was studied by means of proton nuclear magnetic resonance measurements. The jump frequencies of H atoms in the lattice were deduced, from dipolar spin-lattice relaxation rates, by applying the BPP model. In PdHy, the temperature dependence of the spin-lattice relaxation rates was described well by a single-jump process for all H atoms. In Pd1-xAgxHy, the spin-lattice relaxation rate data revealed more than one jump process with differing activation energies. Two and three processes could be separated for x = 0.1 and x = 0.3, respectively. In both alloys, the diffusion process with the lowest activation energy (0.226eV) was comparable to that in pure Pd. Jump processes with higher activation energies occurred more frequently in Pd0.7Ag0.3 than in Pd0.9Ag0.1. This indicated the existence of higher energy barriers for jumps between O-sites in Ag-rich environments. Direct measurements of the long-range diffusion coefficients were performed using pulsed-field gradient nuclear magnetic resonance methods at up to 450K. For both Pd1-xAgxHy samples, the temperature dependence of the diffusivity was well-represented by a single Arrhenius law:

x = 0.1:     D (m2/s) = 3.0 x 10-7 exp[-0.23(eV)/kT]

x = 0.3:     D (m2/s) = 2.1 x 10-7 exp[-0.26(eV)/kT]

The diffusivities which were deduced from the jump frequencies of the H atoms were in good agreement with the pulsed-field gradient results and with measurements performed using the time-lag technique.

H.Züchner, H.Barlag, G.Majer: Journal of Alloys and Compounds, 2002, 330-332, 448-53