Nuclear magnetic resonance study of hydrogen motion in C15-type TaV2Hx (x ≤ 0.18)

Abstract Nuclear magnetic resonance (NMR) measurements of the 1 H and 51 V spin-lattice relaxation rates in C15-type TaV 2 H x ( x =0.06, 0.10 and 0.18) have been performed over the temperature range 11–424 K. The experimental results are consistent with a coexistence of two H jump processes with well-separated characteristic frequencies. The slower jump process responsible for the long-range H diffusion is satisfactorily described by the Arrhenius law with the activation energy of 0.22 eV. In the studied range of low H concentrations, the localized hydrogen motion (associated with the faster jump process) is found to be extremely rapid, giving rise to the proton spin-lattice relaxation rate peaks at T ≤50 K. The reasons for the absence of low-temperature ultrasonic attenuation peaks due to localized H motion in the same TaV 2 H x samples are discussed.