PHASE-STABILITY AND NEUTRON-DIFFRACTION STUDIES OF LAVES PHASES ZR(CR(1-X)M(X))(2) WITH M=MN, FE, CO, NI, CU AND 0-LESS-THAN-X-LESS-THAN-0.2 AND THEIR HYDRIDES

Laves phases of composition Zr(Cr(1-x)M(x))(2) with M=Mn, Fe, Co, Ni, Cu and 0<x<0.2 have been synthesized with the hexagonal C14- and/or cu bic C15-type structures. By X-ray and neutron diffraction we have dete rmined the structures of the alloys and in particular the sites for th e 3d metal substitution. The position of the hydrogen atoms in the str uctures and the occupation of the different sites of the hydrides have been determined. Purity and quality of polycrystalline alloys have be en checked by using electron microscopy scanning and energy-dispersive X-ray techniques. The effects of the M-Cr substitution have been stud ied for phase stability, maximum hydrogen content and hydrogen site st ability and analysed in view of applications as electrodes in H-M batt eries.