Decomposition of single-source precursors under high-temperature high-pressure to access osmium–platinum refractory alloys

Abstract

Thermal decomposition of (NH4)2[OsxPt1-xCl6] as single-source precursors for Os-Pt binary alloys has been investigated under ambient and high pressure up to 40 GPa. Thermal decomposition of mixed-metal (NH4)2[OsxPt1-xCl6] precursor in hydrogen atmosphere (reductive environment) under ambient pressure results in formation of β-trans-[Pt(NH3)2Cl2] and α-trans-[Pt(NH3)2Cl2] crystalline intermediates as well as single and twophase Os-Pt binary alloys. For the first time, direct thermal decomposition of coordination compound under pressure has been investigated. A formation of pure metallic alloys from single-source precursors under pressure has been shown. Miscibility between fccand hcpstructured alloys has been probed up to 50 GPa by in situ high-pressure X-ray diffraction. Miscibility gap between fccand hcp-structured alloys does not change its positions with pressure up to at least 50 GPa.

Osmium and OsOx nanoparticles: an overview of syntheses and applications

“…In addition to the examples already mentioned above, for instance in Figure 6, various alloyed nanoparticles have been reported such as IrOs 14 , PtOs 97 , OsB 2…”

Modification of Lu's (2005) high pressure model for improved high pressure/high temperature extrapolations. Part II: Modeling of osmium–platinum system at high pressure/high temperature

“…Very recently, experiments were conducted allowing to investigate Os-Pt phase diagram up to 50 GPa [9]. The main finding is the absence of significant changes of the mutual solubilities with pressure.…”

“…Such trend has been confirmed for Ir-Os and Ir-Re binary alloys, where metals have close atomic volumes and significantly different compressibility (Ir-Os binary alloys) or different atomic volumes and nearly identical compressibility (Ir-Re binary alloys) [5][6][7][8]. Os-Pt system represents significant differences in atomic volumes and compressibility and shows that upon compression the two-phase field becomes more narrow with pressure [9]. The aim of the present work is to provide a thermodynamic description of this system by the Calphad method including the modeling at high pressure.…”

“…They agree with the previous reports as far as the solubility of Pt (~11 at.%) in the hcp solid solution is concerned but not concerning the osmium solubility (~44 at.%) in the fcc solid solution. A high pressure experimental study of the system has been recently published by Yusenko et al [9] using samples obtained from single-source inorganic precursors. The data will be compared with our calculations in the discussion section below.…”

“…From the experimental point of view, several platinoid systems at high pressure have already been studied up to 140 GPa at room temperature and upon heating above 3000 °C [5][6][7][8]. Os-Pt system has been also studied up to 50 GPa and 2300 °C [9]. Experimental investigation of binary phase diagrams based on refractory hexagonal close packed (hcp: Os, Re, Ru) metals as the first component and face-centered cubic (fcc: Ir, Pt, Rh) refractory metals as the second component requires careful analysis due to the presence of a two-phase domain between hcp and fcc alloys.…”