Pressure-composition measurements and microstructural analysis of the laves phases Zr(Cr0.5Mo0.2M0.3)(2) with M=Fe, Co, Ni

The Laves phases Zr(Cr0.5Mo0.2M0.3)(2) with M=Fe, Co, Ni have been synthesised in the hexagonal C14 type structure. Hydrogen absorption-desorption isotherms have been determined by pressure-composition isotherms (P-C-T) within the temperature range 298-423 K. We have observed that for more than 50% of chromium substitution, the compounds always have a relatively high capacity (H/M>1). Moreover, some isothermal curves reveal the existence of a sloping plateau. To understand the origin of this plateau, the phase composition and purity of polycrystalline alloys have been checked using SEM and EDX techniques.