Pt2AuCuNiSn, a new noble metal single-phase high entropy alloy

Abstract

A new single-phase noble metal high entropy alloy, Pt2AuCuNiSn, has been obtained at comparatively low temperatures by a solid-state reaction. A Rietveld refinement gave a satisfactory description of the X-ray diffraction data, showing that the compound crystallizes with space group Fm3m, where only one Wyckoff site is occupied. In bulk samples, SEM/EDX measurements gave no indication for chemical inhomogeneities on a μm length scale. Temperature dependent in situ diffraction measurements using high energy (λ ¼ 0.1204 Å) radiation up to 875 K show several transient phases upon heating a mixture of the elements, consistent with results of DSC measurements. The parameter describing the variability of the radii of the constituent atoms, δr, is uncommonly large (δr ¼ 8.7%) and maybe the origin of the instability of this alloy at high temperatures.