Phase components and hydriding properties of the sintered Mg-xwt.% LaNi₅ (x=20-50) composites

Powder mixtures of magnesium and LaNi₅ with nominal composition Mg-x wt.% LaNi₅ (x=20-50) were pressed into pellets and sintered at 973 K for 1 h. After sintering, it was found that when x=20-40 the major phases were pure Mg, Mg₂Ni and La₂Mg₁₇, including small amounts of MgO. Further increasing x to 50, Mg₂Ni and La₂Mg₁₇ remained the major phases but pure magnesium disappeared. In contrast to previously published results, the LaMg₁₂ phase was not found in the above composition range. The phase abundance as a function of composition was quantitatively determined by Rietveld analysis. It was also found that changing the sintering temperature from 723 to 973 K did not change the resultants of the sintered Mg-50 wt.% LaNi₅ composite as well as their relative amounts. All samples were easily activated at 623 K, and their pressure-composition isotherms of hydrogenation were measured at 573 K.