Hydrides of LaNi and CeNi intermetallic compounds

Abstract

The hydriding characteristics of La 7Ni 3, LaNi and Ce 7Ni 3 have been investigated. These compounds form the stable hydrides La 7Ni 3H 19.3, LaNiH 3.85 and Ce 7Ni 3H 19.2. In structural and magnetic investigations La 7Ni 3is found to decompose into LaH 3 and LaNi 5 on rapid hydrogenation. On desorption at elevated temperatures the original La 7Ni 3 structure is reformed. An analogous decomposition is found in Ce 7Ni 3. The enthalpies of formation ΔH have been measured calorimetrically for the hydrides of LaNi compounds. ΔH varies linearly with the LaNi composition, independently of the various compound structures and of structural transformations on hydrogenation. The experimental values of ΔH are described by a phenomenological model. Despite their high hydrogen content, these hydrides are not suitable for use as hydrogen storage materials because of their high stability.