Hydrogenation of Zr6MeX2 intermetallic compounds: Absorption and desorption characteristics, crystal structure, and magnetic properties (Me-Fe, Co, Ni; X-Al, Ga, Sn)

Abstract

We study the process of formation of the hydrides of Zr6MeX2 ternary intermetallic compounds (Me-Fe, Co, Ni; X-Al, Ga, Sn). It is shown that they are characterized by high hydrogen-storage capacity (9.4–10.8 atoms of hydrogen per formula unit). In the process hydrogenation, by the method of X-ray powder diffraction analysis, we revealed the transition of the crystal structure of Zr6MeX2 from the {ie528-1} space group of symmetries into {ie528-2} with doubling of the unit cell in the [001]-direction. The analysis of the crystal structure of Zr6NiAl(Sn)2H x hydrides by using the Rietveld improvement of the data of X-ray powder diffraction analysis shows that it is identical to the structure of Zr6FeAl2D10 deuteride studied earlier by the method of neutron diffraction analysis. The thermal desorption of hydrogen from the synthesized Zr6MeX2 hydrides was observed in the temperature range 400–900°K. The dependence of the magnetic susceptibility of the Zr6FeAl2 compound on temperature is characterized by the presence of a peak at 50°K. The character of these curves undergoes significant changes in the processes of hydrogenation and dehydrogenation of the specimen.