Effect of alloying on thermal conductivity and thermoelectric properties of CoAsS and CoSbS

Abstract

The effect of alloying on the thermoelectric properties of cobaltite, CoAsS, and paracostibite, CoSbS, has been investigated in this study. Density functional theory and the Boltzmann transport equation have been applied to explore the role of phonon–phonon scattering and atomistic scattering due to alloying in phonon transport. An almost 44% reduction in thermal conductivity of CoAs_0.8Sb_0.2S alloy compared to pure CoAsS and an ∼15% reduction in thermal conductivity of CoAs_0.2Sb_0.8S compared to pure CoSbS were found. Simultaneously, the thermoelectric (TE) figure of merit (ZT) increased by ∼11% in p-type CoAs_0.8Sb_0.2S alloy and ∼8% in n-type CoAs_0.2Sb_0.8S alloy as compared to their base pure materials at 800 K. We found that by tuning the composition of CoAs_xSb_(1−x)S alloy, very similar ZT values for both p-type and n-type can be achieved in a large temperature range. We also calculated the TE properties of CoAsSe_(1−x)S_x and CoSbS_(1−x)Se_x alloys. This study will help in designing CoAs_xSb_(1−x)S based alloys for efficient thermoelectric devices.