Pseudobinary intermetallic compounds in Hf2M′–Hf2M″ (M′, M″=Mn, Fe, Ni, Cu) systems and their interaction with hydrogen at high pressures

Abstract

Abstract Ternary alloys in the Hf 2 Ni–Hf 2 Mn, Hf 2 Ni–Hf 2 Fe, Hf 2 Ni–Hf 2 Cu and Hf 2 Fe–Hf 2 Cu systems have been prepared and characterised by X-ray diffraction and pressure–composition isotherm measurements. Single phase compounds have been obtained for all Ni-containing alloys with a general composition of Hf 2 Ni 0.5 M 0.5 . These compounds retained the structure type of parent Hf 2 M intermetallics: cubic Ti 2 Ni type for Hf 2 Ni 0.5 Fe 0.5 and Hf 2 Ni 0.5 Mn 0.5 and tetragonal MoSi 2 type for Hf 2 Ni 0.5 Cu 0.5 . The new hydrides obtained from ternary intermetallics had the composition of Hf 2 Ni 0.5 M 0.5 H x where x =3.1 (M=Cu) and 4.9–5.0 (M=Mn, Fe). Formation of hydride phases from cubic Mn- or Fe-containing compounds occurred without any change in structure type but was accompanied by unit cell volume expansion of 23–24%. In the case of Cu, there was a tetragonal to orthorhombic transformation. An absence of phase transformations in high pressure range of 100 to 2000 atm for new compounds unlike the earlier studied Hf 2 M–H 2 systems has to be noted.