Phase relations and hydrogenation behavior of Sr1−xCaxAl2 (0≤x≤1)

Abstract The phase relations and hydrogenation behavior of Sr1−xCaxAl2 (x=0, 0.1, 0.2, 0.3, 0.5, 0.75 and 1.0) alloys have been studied. It was found that the Zintl phase with orthorhombic structure existed when x≤0.1, which transformed into an unknown hydride phase under hydrogen pressure of 7 MPa at 543 K for 5 days. Increasing x to 0.2, the Zintl phase and C15-type Laves phase coexisted. Both of them transformed into (Sr,Ca)H2 and Al upon hydrogenation. When x≥0.3, however, there was no Zintl phase but the Laves phase was dominant. After hydrogenation, there a certain amount of (Sr,Ca)H2 and Al as well as a large amount of C15 phase remained in hydrogenated Sr0.7Ca0.3Al2, Sr0.5Ca0.5Al2 and Sr0.25Ca0.75Al2. The crystal structure of the binary CaAl2 alloy did not change with hydrogenation.