Complex alloys containing double-mackay clusters and (Sb _1-δZn_δ)₂₄ snub cubes filled with highly disordered zinc aggregates: Synthesis, structures, and physical properties of ruthenium zinc antimonides

A series of cluster-based ruthenium zinc antimonides with a large unit cell were obtained. Their structures were solved by the single crystal X-ray diffraction methods. They crystallize in the cubic space group of Fm3c (No. 226) with cell dimensions of 25.098(3), 24.355(3), 24.307(3), and 24.376(3) Å for Ru₂₆Sb₂₄Zn₆₇ (CA), Ru₁₃Sb ₁₂Zn_83.4 (CB), Ru₁₃Sb_6.29Zn _91.56 (CC), and Ru₁₃Sb_17.1Zn_74.8 (CD), respectively. By all indications, compounds CA and CB are two phases showing pronounced distinctions regarding compositions, lattice parameters, thermal and transport properties, but they are not members of an extended solid solution. Compounds CB, CC, and CD are three members of a same solid solution. Topologically, these four compounds contain face-centered cubic packing of double-Mackay type clusters and (Sb_1-δZn_δ) ₂₄ snub cubes filled with highly disordered zinc aggregates, with or without glue atoms between them. Both phases CA and CB are diamagnetic. There is a difference of ∼170 K between their thermally stable temperatures. CA exhibits rather low thermal conductivity with the value of ∼0.9 W m ^-1 K^-1 at room temperature, which is about one-third that of CB. The electrical resistivity of CB is almost temperature independent. The Seebeck coefficient of CB is small and negative, while that of CA exhibits a complicated temperature dependence and undergoes a transition from p- to n-type conduction around room temperature.