Structural, magnetic, electrochemical and hydrogen absorption properties of Gd_yMg_2-yNi_4-xAl_x compounds with 0.4 < y < 2 and 0 < x < 1.2

A solid solution with the C15b structure (MgCu₄Sn-type) exists as a series from GdNi₂ to Gd_0.4Mg_1.6Ni₄ (Gd_0.2Mg_0.8Ni₂). These compounds were successfully elaborated by (i) Mechanical Alloying (MA) and (ii) melting followed by a subsequent annealing. It was also possible to synthesise the solid solution GdMgNi_4-xAl_x with x up to 1.2. The product is highly dependent on the elaboration route which induces a drastic change in both chemical and physical properties (i.e. magnetism, electrochemistry, and structural disorder). A direct relationship between all these property modifications was established. Finally, it is shown that different compounds have different behaviours towards hydrogen sorption regarding both the hydrogen uptake and the thermodynamic results.