Large enhancement of thermoelectric properties of CoSb3 tuned by uniaxial strain

Skutterudite (CoSb3), as a promising thermoelectric material for medium-temperature applications, has attracted considerable interest. However, improving its thermoelectric properties is still an important problem. In this work, first-principles calculations combined with semiclassical Boltzmann theory are adopted to investigate the electronic transport and thermoelectric properties of CoSb3 under external strain. It is found that both tensile strain and compressive strain reduce the bandgap of the CoSb3 system and influence the Co_d orbitals near the Fermi level. Further, the steepness of the valence band near the Fermi level along the M-G and G-R directions are changed by external strain to different extents, which directly affects the Seebeck coefficient and the ratio of conductivity to relaxation time; both of these values are optimized under tensile and compressive strain. Therefore, the power factor of CoSb3 is greatly enhanced under external strain. At 700 K, the maximum power factors under strains of - 1% and 3% are 23.77% and 47.63% higher than those without strain, respectively. Thus, the thermoelectric properties of CoSb3 can be greatly improved by external strain.(C) 2022 Elsevier B.V. All rights reserved.