Synthesis of new hydrides with cubic structures in Mg-Ca-Ni systems by using high pressure

Phases and thermal stability of new hydrides synthesized by using under a h igh pressure of 5 GPa in Ca-Mg-Ni-H systems were studied The high-pressure synthesis was carried out at 1073 K-1223 K for 2 h under 5 GPa by using an anvil-type apparatus. A series of (Ca1-xMgx)(2)NiHdelta was found to form s olid solution in the range of x = 0-0.4. This hydride decomposed around 646 K regardless of Mg content. In CaH2-X%MgH2 systems, hydrides with BCC stru cture were obtained in the range of X = 50-67. Lattice constant of the BCC phase decreased from 0.4032(9) nm (X = 50) to 0.3988(3) mn (X = 67) with in creasing Mg content. The decomposed temperature of the BCC phase increased from 650 K (X = 50) to 673 K (X = 67) with increasing Mg content, in other words, with decreasing the lattice constant of BCC phase.