Effects of PbS doping on thermal conductivity of n-type CoSb3

Additional PbS doping of heavily doped n-type Co_1-xM _xSb₃ (M=Pd/Pt) has been studied to reduce the thermal conductivity of the material. Although the heavily doped n-type material has good electrical properties, the thermal conductivity is relatively high (about 0.06 W cm^-1 K^-1). If PbS particles are dispersed throughout the host material, they can be expected to act as phonon scattering centers. Polycrystalline samples were prepared by hot pressing or spark plasma sintering the admixture of Co_1-xM_xSb₃ (M=Pd/Pt) and PbS fine powders. Samples were characterized by X-ray diffraction, electron probe microanalysis, and optical microscope observation. Measurements of the electrical conductivity, the Hall coefficient, the Seebeck coefficient, and the thermal conductivity were performed to study the influence of PbS doping on the electrical and thermoelectrical properties. It was found that PbS particles were uniformly dispersed throughout Co_1-x M_xSb₃ (M=Pd/Pt) host without any decomposition. About 30% reduction of the thermal conductivity can be achieved by additional PbS doping, keeping good electrical properties. This can be attributed to the phonon scattering effect of PbS particles. As a result, the thermoelectric figure of merit of the material increases to more than 1×10^-3 K^-1