Compounds for H storage, of AB5 and AB2 type, were characterized by using positron annihilation lifetime spectroscopy. It was shown that they contained no constitutional

vacancies, and that deviations from the stoichiometric compositions were all compensated by antistructure atoms. The positron lifetimes of fully-annealed LaNi5-xAlx alloys exhibited a good correlation with their H desorption pressures. On the other hand, surprising numbers of vacancies and dislocations were found to be generated during the first H absorption stage of LaNi5.

Positron Annihilation Study of Lattice Defects Induced by Hydrogen Absorption in Some Hydrogen Storage Materials. Y.Shirai, H.Araki, T.Mori, W.Nakamura, K.Sakaki: Journal of Alloys and Compounds, 2002, 330-332, 125-31