Synthesis of Sr2AlH7 by ball milling followed by hydrogenation

The hydride Sr2AlH7 was synthesized by ball milling of the alloy consisting of Sr and Al (2:1) under hydrogen at 150 rpm for 10 h followed by hydrogenation or sintering at 533 K for 2 days. The yield of Sr2AlH7 in the hydrogenated product was 66 wt.%, which is larger than that in the sintered product. However, the mass fraction of Al in the milled samples decreased largely when the Sr2Al alloy was milled at 300 rpm for 50 h or longer. In such a case, the Sr2AlH7 hydride cannot be obtained during the subsequent hydrogenation.