High pressure synthesis of novel compounds in Mg-TM systems (TM = Ti-Zn)

High pressure synthesis under 6GPa 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 F $(4) over bar $ 3m with a lattice parameter of alpha = 1.9987(1) nm was synthesized as a new compound at 1173 K for 8 h under 6GPa. it decomposed to Mg and Mg2Ni phase at 545K as exothermic reaction. In Mg-Cu systems, two unreported phases were synthesized at 1073K for 8h under 6GPa. 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 MgCu and MgCu2 phases at 500 K and the Mg-51 Cu-20 compound did to Mg and Mg2Cu phase at 430 K.