Systematic Exploration of the Gd–Os–Ge Ternary System with Magnetic and Transport Property Studies of Highly-Disordered Quasiskutterudite Gd3.4Os4Ge12.6

The isothermal section of the ternary Gd–Os–Ge diagram at 800 °C was investigated with samples synthesized and characterized using scanning electron microscopy and X-ray diffraction. The collected data were used to construct a ternary phase diagram, providing insight into the phase formation trends and potential regions of phase stability. Four novel ternary compounds in this system, namely, Gd 2 OsGe 2 (Sc 2 CoSi 2 -type), GdOs 1- x Ge 2 (CeNiSi 2 -type), Gd 2 Os 3 Ge 5 (U 2 Co 3 Si 5 -type) and Gd 3.4 Os 4 Ge 12.6 (Yb 3 Rh 4 Sn 13 -type) were reported, showing a lack of Os-rich phases. The physical properties study of the Gd 3.4 Os 4 Ge 12.6 include magnetic and transport properties. The site-disordered Gd 3.4 Os 4 Ge 12.6 (Yb 3 Rh 4 Sn 13 -type) exhibits possible antiferromagnetic correlations and an unusual increasing electrical conductivity trend isuggesting possible semimetallic properties with a zT value of 0.05, one of the highest figures of merit found among ordered Yb 3 Rh 4 Sn 13 -type compounds. The cage-like structure of skutterudite-related Yb 3 Rh 4 Sn 13 -type compounds provides a promising investigation for its thermoelectric properties, as it has large internal disorder from atomic mixing, site splitting, and a cage of neighboring atoms to scatter heat-carrying acoustic phonons, both favorable for low thermal conductivity. The intermetallic phases of this exploration were investigated with density functional theory for their respective electronic structures featuring strong Os–Ge bonding, resulting in different Os-centered polyhedra throughout the Ge-rich phase phases.