Discussion (1)
The metallographic appearance of the as prepared samples was single phase.
The samples subjected to electrochemical hydriding show a modification of the crystal structure (Fig. 1 ) and deep changes of magnetic properties (Fig. 2, 3), (Tab. 1).
The hydrogenation process doesn’t change the cubic MgCu2 structure type of GdCo2 the lattice constant expands markedly from a = 0.7250 nm in the parent compound GdCo2 to a = 0.7689 nm for the 20 hours hydrogenated sample; and its behaviour with the hydrogenation time is similar to the one obtained in ref 4, where a small lattice expansion is found for xə.2 followed by a much larger one, for xɭ.6. The lines in the diffraction patterns (Fig. 1 ) of the hydrides are considerably broadened and less intense than the ones observed in the parent compound. This behaviour may be ascribed to a considerable deformation of the original lattice.
in accordance with other authors [4] the sample electrochemically hydrogenated for only 2 hours displays a decrease in the values of both saturation magnetisation and spontaneous magnetisation, while for higher hydrogenation times the samples exhibit an increase of both saturation magnetisation and spontaneous magnetisation (Fig ). Taking as a reference trend the magnetisation data reported in [4] we can estimate for the sample electrochemically hydrogenated for 20h an hydrogen content x of nearly x=1.7.