Optimizing thermoelectric performance of CoSbS0.85Se0.15 by doping 3d transition metal ions M (M = Cr, Mn, Fe and Ni)

Abstract

Transitional metal compound CoSbS attracted much attention as a thermoelectric material in the past decades. The configuration of the transition metal octahedra has a close relationship with the thermoelectric performance. This study reports the optimized thermoelectric performance of CoSbS through tuning Co octahedra distortion. The substitution of M (M ​= ​Cr, Mn, Fe and Ni) on Co sites could remarkably reduce the lattice thermal conductivity, and typically, Cr substitution endows the lowest lattice thermal conductivity owing to its strongest effect on the octahedra distortion, whereas Ni substitution induces to a relatively weak octahedra distortion at the same substitution level. Additionally, band structure calculations demonstrate that Ni-3d orbitals contribute shallow impurity levels near the conduction band minimum, strikingly increasing the carrier concentration and power factor. As a result, CoSbS0.85Se0.15 with Ni substitution on Co sites exhibits a much higher thermoelectric performance compared with the other counterparts. Furthermore, by optimizing Ni content, a maximum zT value of 0.52 ​at 876 ​K was achieved in Ni0.10Co0.90SbS0.85Se0.15. This study provides an exemplary approach to optimize the thermoelectric performance via polyhedral distortion.