High Compressibility of Synthetic Analogous of Binary Iridium–Ruthenium and Ternaryiridium–Osmium–Ruthenium Minerals

Hcp–Ir_0.24Ru_0.36Os_0.40 and fcc–Ir_0.84Ru_0.06Os_0.10 ternary alloys as well as binary hcp–Ir_0.33Ru_0.67 and fcc–Ir_0.75Ru_0.25 alloys were prepared using thermal decomposition of [Ir_xRu_1-x(NH₃)₅Cl][Os_yIr_(1-y)Cl6] single-source precursors in hydrogen flow below 1070 K. These single-phase alloys correspond to ternary and binary peritectic phase diagrams and can be used as synthetic models for rare iridosmine minerals. Thermal decomposition of parent bimetallic precursor [Ir(NH₃)₅Cl][OsСl₆] has been investigated using in situ powder X-ray diffraction in inert and reductive atmospheres. In reductive atmosphere, [Ir(NH₃)₅Cl][OsСl₆] forms (NH₄)₂[OsСl_6<] as crystalline intermediate; Ir from its cationic part is reduced by hydrogen with a formation of defect fcc -structured metallic particles; the final product is a metastable hcp I.0.5Os_0.5 alloy. In inert atmosphere, the salt decomposes at higher temperature without a formation of any detectable crystalline intermediates; two-phase fcc+hcp mixture forms directly above 800 K. Room temperature compressibility up to 50 GPa has been studied for all prepared alloys in diamond anvil cells. Hcp–Ir_0.24Ru_0.36Os_0.40 (B0 = 362(4) GPa, B0' = 4.8(2)) and fcc–Ir_0.84Ru_0.06Os_0.10 (B0 = 302(7) GPa, B0' = 6.4(5)) ternary alloys as well as hcp–Ir_0.33Ru_0.67 (B0 = 332(2) GPa, B0' = 5.4(1)) and fcc–Ir_0.75Ru_0.25 (B0 = 316(1) GPa, B0' = 5.1(1)) binary alloys do not show any phase transitions upon compression at room temperature. In contrast with other investigated ultra incompressible refractory alloys with osmium and iridium, hcp–Ir_0.33Ru