Isotope effect on the thermodynamic and structural properties of Y1−yRyFe2(H,D)x(γ) compounds (R = Tb, Er, Lu; 4.0 ≤ x(γ) ≤ 4.5)

Thermodynamic and structural properties of Y1−yRyFe2H(D)x(γ) compounds (R = Tb, Er, Lu, 4.0 ≤ x(γ) ≤ 4.5) have been investigated using Sieverts method and X-ray diffraction (XRD) at 298 K. The D for H substitution induces a lowering of the plateau pressure, a small increase of the γ phase capacity and a decrease of about 1.7 Å3 of the cell volume. Additionally, the anomalous behavior of the plateau pressure versus cell volume observed upon Tb substitution has been explained by a change of the relative position of Y in the lanthanide series upon H(D) absorption.