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Structural and hydrogen sorption properties of RENi4Ga (RE=Gd, Y and Tb) alloys

Alloys of the composition RENi4Ga (RE=Gd, Y, Tb) were prepared and studied by x-ray powder diffraction. It was found that the crystal structure of the prototype binary compounds RENi5 (space group P6/mmm, CaCu5 type) is preserved in the ternary region. All alloys were exposed to hydrogen gas. It was foud that they react readily with hydrogen to form hydrides with up to 3.6 hydrogen atoms per alloy formula unit. Thermodynamic parameters, the entropy and the enthalpy have been extracted from the pressure-composition-desorption isotherms. It was found that substitution of gallium for nickel decreases the equilibrium pressure and the hydrogen capacity of the corresponding binary alloys.

Rare earth intermetallics; metal hydrides; crystal structure

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