Diffusion of hydrogen isotopes and their mutual perturbation in Ti 0.33V 0.67H xD y ( x+ y≈0.9) studied by 1H and 2H NMR

Abstract

Ti 0.33V 0.67H x D y ( x+ y≈0.9) alloys have been studied by means of X-ray powder diffraction (XRD), differential scanning calorimetry (DSC) and 1H and 2H NMR. The crystal structures are body-centered-cubic (bcc) dominantly, being mixed with a face-centered-cubic (fcc) phase. A phase transition similar to that from the δ D phase to the α D phase in the V–D system is observed in all the samples except for the protide. H and D are considered to occupy tetrahedral sites. The temperature and frequency dependence of spin-lattice relaxation times T 1 of 1H and 2H has been analyzed by Bloembergen–Purcell–Pound equations with a distribution of correlation times, and parameters of hydrogen diffusion are estimated. The mean activation energy for D diffusion ( E D) is higher than that for H diffusion ( E H). E H is constant while E D increases slightly with the [D]/[H] ratio. The distribution of the correlation times increases as the [D]/[H] ratio decreases.