Hydrogen sorption behavior of some Pd-containing compounds

New pseudobinary Zr(PdxV1−x)2, x = 0.1, 0.15, 0.2, intermetallic compounds have been synthesized and characterized by X-ray diffraction and their shear, G, and bulk, B, moduli have been measured. Hydrogen absorption isotherms of the x = 0.1 and 0.2 alloys have been determined at temperatures between 200 °C and 500 °C in the pressure range 10−7-1.3 atm. An increase of the Pd content causes a decrease of both the hydrogen absorption capacity and the stability of the corresponding hydrides. The latter behavior is attributed mainly to the Pd-induced increase of the stability of the starting intermetallics (rule of reversed stability). A combined effect of the heats of alloy formation, ΔHalloy, and the crystal cell volumes, V, on the stabilities of the hydrogenated compounds is shown for Zr(PdxV1−x)2 and Zr(AlxV1−x)2 in terms of correlation factor ΔHalloy + bV, where b is a fitted constant. The decrease of the hydrogen absorption capacity with x in Zr(PdxV1−x)2 correlates well with an increase of the G/B ratio, as previously suggested. We have also tried to produce and hydrogenate alloys of the systems Ti(PdxNi1−x)3, Zr(PdxFe1−x)2 and Zr(PdxNi1−x)3 but did not find significant hydrogen absorption.