Face-Centered Cubic Refractory Alloys Prepared from Single-Source Precursors.

Kirill V Yusenko,Maxim Bykov,Alexander Sukhikh,Tymofey Fedotenko,Sergey A Gromilov,Michael Hanfland,Saiana Khandarkhaeva,Leonid S Dubrovinsky

doi:10.3390/ma13061418

Abstract

Three binary fcc-structured alloys (fcc–Ir0.50Pt0.50, fcc–Rh0.66Pt0.33 and fcc–Rh0.50Pd0.50) were prepared from [Ir(NH3)5Cl][PtCl6], [Ir(NH3)5Cl][PtBr6], [Rh(NH3)5Cl]2[PtCl6]Cl2 and [Rh(NH3)5Cl][PdCl4]·H2O, respectively, as single-source precursors. All alloys were prepared by thermal decomposition in gaseous hydrogen flow below 800 °C. Fcc–Ir0.50Pt0.50 and fcc–Rh0.50Pd0.50 correspond to miscibility gaps on binary metallic phase diagrams and can be considered as metastable alloys. Detailed comparison of [Ir(NH3)5Cl][PtCl6] and [Ir(NH3)5Cl][PtBr6] crystal structures suggests that two isoformular salts are not isostructural. In [Ir(NH3)5Cl][PtBr6], specific Br…Br interactions are responsible for a crystal structure arrangement. Room temperature compressibility of fcc–Ir0.50Pt0.50, fcc–Rh0.66Pt0.33 and fcc–Rh0.50Pd0.50 has been investigated up to 50 GPa in diamond anvil cells. All investigated fcc-structured binary alloys are stable under compression. Atomic volumes and bulk moduli show good agreement with ideal solutions model. For fcc–Ir0.50Pt0.50, V0/Z = 14.597(6) Å3·atom−1, B0 = 321(6) GPa and B0’ = 6(1); for fcc–Rh0.66Pt0.33, V0/Z = 14.211(3) Å3·atom−1, B0 =259(1) GPa and B0’ = 6.66(9) and for fcc–Rh0.50Pd0.50, V0/Z = 14.18(2) Å3·atom−1, B0 =223(4) GPa and B0’ = 5.0(3).

Highlights

High-entropy alloys were prepared using conventional melting of pure metals.catalytic applications as well as preparation of high-entropy alloys based on metals with ultra-high melting points need the development of new techniques for a preparation of high-entropy alloys as fine nanostructured powders
The strategy requires a synthesis of coordination compounds from water solutions and their further thermal decomposition in a hydrogen flow based on the following principle general scheme [1]: in water solution: a[Ir(NH3 )5 Cl]Cl2 + b[Rh(NH3 )5 Cl]Cl2 + (1-a-b)[Ru(NH3 )5 Cl]Cl2 +
We report synthesis of fcc–Ir0.50 Pt0.50, fcc–Rh0.66 Pt0.33 and fcc–Rh0.50 Pd0.50 binary alloys from [Ir(NH3 )5 Cl][PtCl6 ], [Ir(NH3 )5 Cl][PtBr6 ], [Rh(NH3 )5 Cl]2 [PtCl6 ]Cl2 and

Summary

Introduction

High-entropy alloys were prepared using conventional melting of pure metals. Single-source precursors strategy has been applied to access high-entropy alloys based on platinum group metals. Single-phase fcc- and hcp-structured high-entropy alloys were tested under extreme conditions to characterize their pressure and temperature stability. Due to their compositional complexity, a little was investigated regarding a mechanism of their formation from single source precursors. It has been shown that all known platinum group alloys do not show any temperature and/or pressure induced phase transitions Such a finding makes platinum group alloys important as stable materials with a unique phase and structural stability under extreme conditions. Thermal expansion and pressure compressibility for known refractory high-entropy alloys can be validated with experimental data obtained for fcc-structured refractory binaries

Materials and Methods

Results and Discussion

Crystal

Preparation of fcc-Structured fcc‐Structured Binary

Conclusions