High-Pressure Synthesis of Novel Hydride in Mg-Ni (-H) System

Abstract

A novel hydride was synthesized in Mg-Ni-H system by high pressure technique using a cubic-anvil-type apparatus. Crystal structure, thermal stability and hydrogen content of the hydride were studied. The novel hydride with a composition of MgNi2Hy was synthesized at 973 K for 2 h under the pressure of more than 2 GPa, and was found to exhibit the body-centered tetragonal structure (space group I4=mmm, No.139) with lattice parameters of a ¼ 0:327ð3Þ nm, c ¼ 0:878ð9Þ nm. Moreover, this hydride could be synthesized from each starting material, such as MgNi2 high pressure phase, MgNi2 (C36) and mixture of MgH2-x mol% Ni (x ¼ 65{70). Its hydrogen content was estimated to be 2.23 mass% from fusion analysis and corresponding chemical formula was found to be MgNi2H3:2. This hydride was decomposed into MgNi2 (C36) over 460 K, and has solubility of Ni content and thermal stability of the novel hydride was decreased with increasing Ni content. [doi:10.2320/matertrans.47.1957]