Nuclear magnetic resonance measurements were made, using resonance frequencies ranging from 13 to 90MHz at 20 to 420K, of the proton spin-lattice relaxation rate in A15-type Nb3AlHx, where x was equal to 0.13, 1.77 or 2.75. The experimental results were analyzed in order to evaluate the Korringa contributions to the relaxation rate and to the H diffusion parameters. It was found that the electronic contribution to the relaxation rate decreased with increasing H content. The effective activation energies for H diffusion which were deduced from the high-temperature relaxation-rate data were equal to 0.21eV for x = 0.13, and equal to 0.30eV for x = 1.77 and 2.75. The behaviour of the relaxation rate below 270K, for x = 1.77 and 2.75, suggested that at least 2 frequency scales of H-hopping coexisted. It was shown that the structure of the sub-lattice of interstitial d-sites (partially occupied by H) was consistent with the coexistence of 2 characteristic jump-rates for H atoms.

Nuclear Magnetic Resonance Study of Hydrogen Diffusion in A15-Type Nb3AlHx. A.V.Skripov, A.V.Soloninin, A.P.Stepanov, V.N.Kozhanov: Journal of Physics - Condensed Matter, 2000, 12[46], 9607-16