Impurity Removal Leading to High-Performance CoSb-Based Skutterudites with Synergistic Carrier Concentration Optimization and Thermal Conductivity Reduction.

Thermoelectric properties of CoSb-based skutterudites are greatly determined by the removal of detrimental impurities, such as (Fe/Co)Sb, (Fe/Co)Sb, and Sb. In this study, we use a facile temperature gradient zone melting (TGZM) method to synthesize high-performance CoSb-based skutterudites by impurity removal. After removing metallic or semimetallic impurities (Fe/Co)Sb, (Fe/Co)Sb, and Sb, the carrier concentration of TGZM-CeFeCoSb can be reduced to 1.21 × 10 cm and the electronic thermal conductivity dramatically reduced to 0.7 W m K at 693 K. Additionally, removing these impurities also effectively reduces the lattice thermal conductivity from 7.2 W m K of cast-CeFeCoSb to 1.02 W m K of TGZM-CeFeCoSb at 693 K. As a consequence, TGZM-CeFeCoSb approaches a high power factor of 11.7 μW cm K and low thermal conductivity of 1.72 W m K at 693 K, leading to a peak of 0.48 at 693 K, which is 10 times higher than that of cast-CeFeCoSb. This study indicates that our facile TGZM method can effectively synthesize high-performance CoSb-based skutterudites by impurity removal and set up a solid foundation for further development.