Ternary skutterudites: Anion ordering and thermoelectric properties

The ternary skutterudites AB_1.5Q_1.5 (A = Co, Rh, Ir, B = Ge, Sn and Q = S, Te) have been synthesized and structurally characterised. Powder diffraction data are consistent with the presence of anion ordering, which results in a lowering of the symmetry from cubic to rhombohedral. Instead of the rectangular anion rings characteristic of binary skutterudites, the structure of these ordered skutterudites contains diamond-like heteronuclear B₂Q₂ rings. Their electrical transport properties are consistent with semiconducting behaviour, and large values of the Seebeck coefficient have been observed for several of these materials. While their large electrical resistivities might make these materials unsuitable for thermoelectric applications unless significant improvements can be achieved by doping, these materials also exhibit significantly lower thermal conductivities than their binary counterparts. © 2008 Materials Research Society.