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Magnesium I 1200Synthesis and Decomposition of Perovskite-Type Hydrides, MMgH3 (M: Na, K, Rb). -The title compounds are synthesized by ball milling using powders of NaH, KH, Rb, and MgH2 as starting materials followed by heat treatment (673 K, 1.0 MPa H2, 3 h). NaMgH3 decomposes in a two-step reaction, whereas KMgH3 decomposes in a single-step reaction. RbMgH3 seems to decompose in a two-step reaction. The phase stability of these perovskite-type hydrides changes in the order RbMgH 3 > KMgH 3 > NaMgH 3 . -(KOMIYA*, K.; MORISAKU, N.; RONG, R.; TAKAHASHI, Y.; SHINZATO, Y.; YUKAWA, H.; MORINAGA, M.; J. Alloys

Pure Ca(AlH4)2 is synthesized and its decomposition reactions are investigated in a fundamental manner. The XRD profile observed is in good agreement with the one reported by Fichtner et al. From TDS measurements, Ca(AlH4)2 appears to decompose into CaH2+2Al+3H2 in three steps. The peak temperature of the first reaction is about 470K which is higher than that for Mg(AlH4)2 (about 450K), indicating that Ca(AlH4)2 is more stable hydride than Mg(AlH4)2. In addition, the catalysis of TiCl3 is doped into Ca(AlH4)2 by ball milling under a hydrogen gas atmosphere and catalytic effects on the decomposition properties are investigated.