X-ray diffraction peak broadening and degradation in LaNi 5-based alloys

Abstract

Peak broadening in X-ray powder diffraction (XRD) profiles of LaNi 5-based alloys after hydriding and dehydriding processes, was investigated in order to clarify the relation between the formation of lattice strain and degradation by the hydriding–dehydriding cycling. The degree of peak broadening in XRD profiles was calculated by the Rietveld method and hydrogen capacity was evaluated from P-C isotherms for LaNi 5 and LaNi 5− α M α (M: Mn, Fe, Cu, Al; α=0.25, 0.5) after activation and after 1000 hydriding-dehydriding cycles. It was found that an anisotropic peak broadening parameter expressing lattice strain after activation has a linear relation with the decrease in hydrogen capacity. The above parameter is a suitable indicator of the ease of degradation in LaNi 5-based alloys.