Deuterium diffusion in vanadium deuterides(VDx; 0.4 <= x <= 0.6) studied by H-2 NMR

摘要

Sites and dynamics of deuterium in VD0.50 as well as in VD0.40 and VD0.57 have been studied by means of X-ray diffraction, differential scanning calorimetry and H-2 NMR. VD0.40 consists of the body-centered-cubic (hcc) alpha(D) and body-centered-tetragonal (bct) beta(D) phases at room temperature and only the octahedral (O) sites are occupied in the beta(D) phase. On the other hand, in VD0.50, consisting of the bct beta(D) phase at room temperature, the O site is dominantly occupied with a small occupancy of the tetrahedral (T) sites in the beta(D) phase. VD0.57 is composed of the hcc alpha(D) (a high-deuterium-concentration phase of the alpha(D) phase) and bct beta(D), phases at D room temperature, and the occupancy of the T sites is observed. The mean activation energy (ED) of the deuterium diffusion is much larger for the O sites than for the T sites and the diffusion is also much slower in the O sites. The mean E-D Values for the O sites are almost the same in the beta(D) phase of VD0.40 and VD0.50, although the distribution of the mean residence time is much larger in VD0.50 than in VD0.40. (C) 2003 Elsevier Inc. All rights reserved. [References: 27]