High-pressure AB(2) metal hydrides with low hysteresis

The effect of minor substitution for Mn on the basic hydriding properties o f Ti0.95Zr0.05Cr1.2Mn0.7X0.1 (X = Mn, Fe, Co or V) has been studied at 20 a nd 60 degrees C in order to find alloy-hydrogen systems for high-pressure a pplications in which high capacity, low hysteresis and flat pressure-compos ition-isotherm (PCI) plateaus are required. Samples have been synthesized b y arc melting, and characterized by X-ray diffraction (XRD) and volumetric PCI measurements. Experimental evidence shows that even a small amount of V practically eliminates hysteresis while at the same time the PCI plateau s lopes increase. Co-substitution also decreases hysteresis and keeps the PCI plateaus flat, but Fe-substitution does not seem to have any favourable ef fect on the basic hydriding properties. Possibility to study the relationsh ip between hysteresis effect of high-pressure hydrides and their crystal st ructure is discussed. (C) 2000 Kluwer Academic Publishers.