The structural, magnetic, hydrogenation and electrode properties of REMg2Cu9−xNix alloys (RE=La, Pr,Tb)

The LaMg2Cu9, PrMg2Cu9, LaMg2Cu4Ni5, PrMg2Cu4Ni5 and TbMg2Cu6Ni3 alloys were prepared for the investigations of crystal structure, magnetic and hydrogen storage properties. The magnetic properties of several REMg2Cu9−xNix compounds have been studied up to 9 T and from 2 to 300 K. Tb compounds show a ferrimagnetic (with Ni) or antiferromagnetic (without Ni) behaviour, which can be attributed to the Tb magnetic structure. At high temperature a paramagnetic Curie Weiss behaviour is observed and the effective moment corresponds to that of Tb. A magnetic contribution of Pr moment is observed in both Pr compounds, with larger magnetization for PrMg2Cu4Ni5 and a transition at 3 K. The hydrogen absorption occurs at 95 bar for LaMg2Cu9 (3 H f.u.−1) and above 2 bars for LaMg2Cu4Ni5 (1.6 H f.u.−1). The effect of Cu-Ni substitution on the electrochemical properties of LaMg2M9 ternary alloys was investigated leading to maximum discharge capacity of 250–310 mAh g−1.