High Pressure Synthesis of Novel Compounds in Mg-TM Systems (TM = Ti∼Zn)

Abstract

High pressure synthesis under 6 GPa using a cubic-anvil-type apparatus were applied to investigation of new compounds in Mg-TM systems. The crystal structure, thermal stability and reactivity with hydrogen for the newly synthesized compounds were studied. The Mg₄Ni compound belonging to space group F43m with a lattice parameter of a = 1.9987(1) nm was synthesized as a new compound at 1173 K for 8 h under 6 GPa. It decomposed to Mg and Mg₂Ni phase at 545 K as exothermic reaction. In Mg-Cu systems, two unreported phases were synthesized at 1073 K for 8 h under 6 GPa. The one is the MgCu compound which has CsCl-type structure with a lattice parameter of a = 0.31616(7) nm and the other is Mg₅₁Cu₂₀ belonging to space group Immm with a lattice parameter of a = 1.3929(7) nm, b = 1.428(1) nm and c = 1.392(1) nm. The MgCu compound decomposed to Mg₂Cu and MgCu₂ phases at 500 K and the Mg₅₁Cu₂₀ compound did to Mg and Mg₂Cu phase at 430 K.