Enhancing the thermoelectric performance of SnTe-CuSbSe2 with an ultra-low lattice thermal conductivity

Abstract

Alloying SnTe with a well-designed secondary phase, particularly one with low lattice thermal conductivity, serves as an efficient route to realize excellent thermoelectric performance of inferior SnTe with intrinsically large thermal conductivity, which will eventually accelerate PbTe replacement. Herein, the results validate that CuSbSe₂ alloying (SnTe-CuSbSe₂) can optimize the thermal transport properties of SnTe and help to advance the thermoelectric performance. Comprehensive evidence from microstructure characterization manifests that multifarious defects, such as Cu-based nanoprecipitates, dislocations and point defects, are induced into the SnTe matrix after CuSbSe₂ alloying. These defects act as all-scale phonon scattering sources to achieve full-wavelength phonon scattering and promote a significant reduction in lattice thermal conductivity, and an ultra-low lattice thermal conductivity of 0.40 W m⁻¹ K⁻¹ is obtained for the SnTe-5% CuSbSe₂ sample at 823 K. Moreover, deterioration in electrical conductivity also causes a related reduction in electronic thermal conductivity, thereby leading to a substantial reduction in the total thermal conductivity. In addition, the enhancement of m* originating from Cu and Sb doping rises the Seebeck coefficient in SnTe and guarantees a relatively competitive power factor. As a result, based on the significant reduction in the total thermal conductivity, as well as maintenance of the higher power factor, the SnTe-5% CuSbSe₂ sample achieves a maximum ZT value of 1.1 at 823 K, which is greatly improved compared with the pristine counterpart (ZT = 0.5). These findings also reveal the tremendous prospect of boosting the thermoelectric performance of SnTe through CuSbSe₂ and other I–V–VI₂ compounds alloying.