Modification of the thermoelectric performance in Se alloyed CoSb1-xSexS

Abstract

Paracostibite (CoSbS) consists of earth-abundant and low-cost elements, which has received a lot of attention as a newly developed thermoelectric material. In this report, Se-alloyed CoSbS samples with the composition of CoSb1−xSexS (x ≤ 0.2) have been synthesized by the melting annealing process combined with the spark plasma sintering method. It was found that Se alloying can tune the band gap and impurity conductance activation energy of CoSbS effectively, which leads to an increased carrier concentration and an enhanced power factor. The thermal conductivity was sharply suppressed because Se alloying induced the mass fluctuation and strain field fluctuation. The maximum zT of 0.22 was achieved for CoSb0.9Se0.1S at 823 K, which is about twice that of the pristine CoSbS. In particular, the solid solution CoSb1−xSexS has a higher average zT than that of CoSbS1−xSex prepared by the same method. The research shows that the construction of antisite defect of SeSb in CoSbS is an effective route to optimize its thermoelectric performance.