High-pressure synthesis of novel hydrides in Mg-TM systems (TM = Zr, Nb and Mo)

New hydrides of Mg-TM-H systems, where TM = Zr, Nb and Mo, have been prepared by using cubic-anvil-type apparatus, and their crystal structure and hydrogen content have been investigated. The high-pressure synthesis was performed at 1073-1173 K under 2-5 GPa. In the Mg-Zr-H system, a new hydride Mg ₂Zr ₃H _y with a monoclinic structure (a = 0.8591(1) nm, b = 0.33539(5) nm, c = 0.5816(1) nm, β = 103.06(3)°) was obtained by exposing a mixture of MgH ₂ and ZrH ₂ to pressure of 2 to 5 GPa at 1073 K for 2 h. In the Mg-Mo system, a new hydride Mg ₃MoH ₆ was synthesized by exposing a mixture of MgH ₂ and Mo to 5 GPa at 1173 K for 2 h. The hydride was found to have a hexagonal structure (a = 0.49958(6) nm, c = 0.8840(2) nm). In the Mg-Nb-H system, a new hydride Mg ₄NbH _y was also synthesized by exposing a mixture of MgH ₂ and Nb to 5 GPa at 1073 K for 2 h.