CoSb3-IrSb3 solid solutions: preparation and characterization

Abstract

The binary antimonide compounds of the skutterudite family have a good potential for thermoelectric applications as recent results at the Jet Propulsion Laboratory (JPL) have shown. However, the room temperature thermal conductivity of these materials is about 10 Wm−1K−1 with an estimated 80% contribution from the lattice. To achieve maximum ZT values, the lattice thermal conductivity needs to be lowered. Because the lattice thermal conductivity of solid solutions can substantially decrease due to the addition of point defect phonon scattering (all state of the art thermoelectric materials are solid solutions), a study of the formation of solid solutions between the antimonide skutterudite compounds is of interest. The existence of CoP3‐CoAs3 and CoAs3‐CoSb3 solid solutions was already reported in the literature. The preparation and characterization of both p‐type and n‐type CoSb3‐IrSb3 solid solutions by several techniques is reviewed in this paper. The homogeneity of the samples and the existence of solid solutions were investigated using mass density measurements, X‐ray diffractometry, microprobe analysis and optical microscopy. The thermal conductivity, the electrical resistivity, and the Hall mobility were measured from 25 to 500 °C. Experimental results showed that solid solutions were successfully formed in a wide range of compositions. Some immiscibility was observed but may be due to the preparation conditions. The changes in the thermoelectric properties indicated the influence of a strong point defect scattering, resulting in large decreases in Hall mobility and thermal conductivity. The potential for high ZT values in CoSb3‐IrSb3 solid solutions is discussed.