BaGe8As14: a semiconducting sodalite-type compound

Abstract

A new sodalite-type compound, namely BaGe₈As₁₄ was synthesized via solid-state reactions and structurally characterized with single crystal X-ray diffraction (space group I3m). Vertex-sharing GeAs₄-tetrahedra form β-cages with additional Ge/As-mixed sites located slightly above or below the six-membered rings. The structure is similar to the borate mineral rhodizite. Barium atoms are disordered due to a slight shift off the centers of large β-cages. This partially disordered structure together with a narrow bandgap of 0.43 eV in line with low resistivity (2 × 10⁻² Ω cm), and a high carrier concentration (1.6 × 10²⁰ cm⁻³) at 300 K qualifies BaGe₈As₁₄ as a potential thermoelectric material.