Phase relations and hydrogenation behavior of Sr1-xCaxAl2 (0 <= x <= 1)

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 less than or equal t o0.1, which transformed into an unknown hydride phase under hydrogen pressu re of 7 MPa at 543 K for 5 days. Increasing x to 0.2, the Zintl phase and C 15-type Laves phase coexisted. Both of them transformed into (Sr,Ca)H, and Al upon hydrogenation. When x greater than or equal to0.3, however, there w as no Zintl phase but the Laves phase was dominant. After hydrogenation, th ere a certain amount of (Sr,Ca)H, and Al as well as a large amount of C15 p hase remained in hydrogenated Sr0.7Ca0.3Al2, Sr0.5Ca0.5Al2 and Sr0.25Ca0.75 Al2. The crystal structure of the binary CaAl2 alloy did not change with hy drogenation. (C) 2001 Elsevier Science B.V. All rights reserved.