ICT2014 Abstracts

Co₃Sn₂S₂ adopts the pseudo- two-dimensional Shandite structure in which kagome-like sheets of cobalt and tin atoms, capped by sulphur, are pillared by tin atoms of trigonal anti-prismatic coordination. Although the resistivity of Co₃Sn₂S₂ exhibits metallic behaviour, the Seebeck coefficient is comparatively high. Band structure calculations suggest the origin of this behaviour lies in the presence of narrow bands of predominantly Co d-character in the vicinity of E_F. Using chemical substitution, we have succeeded in tuning E_F within these narrow bands, leading to significant enhancements in the Seebeck coefficient. Indium-substituted phases exhibit ZT of ca. 0.3 at 400 °C. Application of complementary diffraction and spectroscopic techniques reveal partial ordering of tin and indium cations in the series Co₃Sn_2-xIn_xS₂ (0 ≤ x ≤ 2) and that the constituent elements are present in the zero oxidation state.