Investigations on the Correlation between Hydrbgenation and Structural Behaviour of RNi5 Type Storage Materials

摘要

The rare earth pentanickelides LaNi5 and MmNi5 (Mm: Mischmetal typically contains 49La, 32Ce, 13Nd, 4Pr and 2 other rare earths) have been synthesized in the form of amorphous and amorphous like phases, it has been found that the amorphous phases have higher hydrogen storage capacity than their crystalline versions. The variation in the electronic behaviour on hydrogenation has been monitored by investigating the variation of resistivity as a function of time. A very curious result embodied in the observation that the thick (～150nm) and thin (V30nm) films of both LaNi5 and MmNi5 have similar resistivity variations, has been found in the present investigation. The present results suggest that it is the surface characteristics and the variation of density of states (DOS) and not the film thicknesses which eventually decide the electrical resistivity variations on hydrogenation. The details of the influence of surface and the density of states (M-H, H-H interactions) on the hydrogenation behaviour have been described and discussed.