Desorption behaviour of hydrogen in the LaNi4.7Sn0.3-H system

The rate of hydrogen desorption in the LaNi4.7Sn0.3-H system studied by means of the volumetric technique has been found to be controlled by H diffusion. Apparent diffusivities of H were estimated using the spherical model and showed a decrease of D on a transition from the α-solid solution to the β-hydride region (6.7 × 10−10 cm2/s for LaNi4.7Sn0.3H3.2−5.3 and 1.2 × 10−9 cm2/s for LaNi4.7Sn0.3H0.2−0.5 at 298 K). Apparent diffusivity for 3.0 < [H]/[LaNi4.7Sn0.3] < 5.5 is almost independent of H content, while for [H]/[LaNi4.7Sn0.3] < 3.0 it is pronouncedly influenced by the H/M ratio and may be dominated by the frequency factor.