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It is shown that the oxygen-stabilised compounds Zr3Fe(Co)Ox (x = 0–1.0) interact with hydrogen at ambient temperature and pressure forming saturated hydrides with filled Re 3B type structure. The hydrogen storage capacity decreases with increasing oxygen content from 6.7 H/f.u. for Zr3Fe down to 5.35 H/f.u. for Zr3FeO1.0 and from 6.9 H/f.u. for Zr3Co down to 5.3 H/f.u. for Zr3CoO1.0. A small change of the unit cell volumes for the Zr3Fe(Co)Ox parent compounds and a substantial increase of these parameters for the corresponding saturated hydrides were observed with increasing oxygen content. The partial hydrogen-induced lattice expansion, � V/at. H, increases from 2.25 A 3 for Zr3FeH6.7 up to 3.38 A 3 for Zr3FeO1.0H5.35 and from 2.08 A 3 for Zr3CoH6.9 up to 3.25 A 3 for Zr3CoO1.0H5.3. Rietveld refinement using neutron powder diffraction data for Zr 3FeO0.4D6.25 showed a distribution of deuterium atoms and a redistribution of oxygen atoms from octahedral to tetrahedral sites in a similar way as in Zr3NiOxDy. Both 57 Fe Mossbauer spectroscopy and magnetic susceptibility measurements of Fe-containing hydrides indicated weak hydrogen-induced magnetic ordering at low temperatures. The ordering temperatures of Zr3FeO0.2H6.52 and Zr3FeO0.6H6.25 are 105 and 140 K, respectively. © 2004 Elsevier B.V. All rights reserved.

To predict the possibility of formation of η-Zr 4 Fe 2 O x ternary intermetallics of Ti 2 Ni type structure during interaction between ZrFe melt and added oxide, the thermodynamic calculations for ZrFeR x O y systems were done. The influence of oxide addition on the hydrogen absorption properties of Zr 2 Fe alloys was studied.

The hydrogenation of Zr3-xTixV3-yNiyOo.6 (0≤x,y≤1.5) alloys has been studied. Phase-structural characteristics of the as cast alloys and their hydrides have been determined by X-ray powder diffraction. In most of alloys the main phase constituent was found to be oxygen-stabilised η-phase (Zr,Ti)3(V,Ni)3O0.6 with the filled-Ti2Ni structure type. The influence of oxygen on phase composition and hydrogenation properties in the case of partial substitution of Zr and V by Ti and Ni has been discussed.

Hydrogen storage capacity and crystal structure of hydrogen-free Zr3V3O0.6 and its saturated deuteride, Zr3V3OxD9.6, have been studied using both X-ray and neutron powder diffraction. Experimental data together with the geometrical analysis of the crystal structure of the deuteride indicate that oxygen non-stoichiometry plays a significant role in the 2-fold increase of hydrogen storage capacity of Zr3V3O0.6 compared with the stoichiometric oxygenated Zr3V3O.

Zirconium-based Zr-V and Zr-Fe alloys are known to be highly efficient absorbers of low pressure hydrogen. Their working performance is structure-dependent and can be improved by modifying the composition of the basic alloys with doping elements. Particularly promising in this respect are modifications of oxide materials where both H-sorption capacity and hydrogenation activity can be increased substantially, especially when boron or rare earth oxides are introduced into the matrices of Zr-V and Zr-V-Fe[1–3].

Hydrogen absorption and desorption properties of the (Hf,Zr) 2 Fe quasibinary alloys (Ti 2 Ni structure type) and the oxygen-stabilised compound Zr 4 Fe 2 O 0.6 with the filled-Ti 2 Ni type of structure, have been studied and discussed in relation to their phase-structural and chemical composition. The crystallographic characteristics, hyperfine parameters and magnetic properties of the hydrogenated alloys have been determined.