Superparamagnetic Fe₃O₄ nanoparticles remarkably enhance the room-temperature thermoelectric and cooling performance of BiSbTe alloys.

The binary skutterudite CoSb₃ is a narrow bandgap semiconductor thermoelectric (TE) material with a relatively flat band structure and excellent electrical performance. However, thermal conductivity is very high because of the covalent bond between Co and Sb, resulting in a very low ZT value. Therefore, researchers have been trying to reduce its thermal conductivity by the different optimization methods. In addition, the synergistic optimization of the electrical and thermal transport parameters is also a key to improve the ZT value of CoSb₃ material because the electrical and thermal transport parameters of TE materials are closely related to each other by the band structure and scattering mechanism. This review summarizes the main research progress in recent years to reduce the thermal conductivity of CoSb₃-based materials at atomic-molecular scale and nano-mesoscopic scale. We also provide a simple summary of achievements made in recent studies on the non-equilibrium preparation technologies of CoSb₃-based materials and synergistic optimization of the electrical and thermal transport parameters. In addition, the research progress of CoSb₃-based TE devices in recent years is also briefly discussed.

Simultaneously optimizing electrical and thermal transport properties of bulk thermoelectric materials remains a key challenge due to the conflicting combination of material traits. Here, we have explored the electrical and thermal transport features of In-filled CoSb₃ through X-ray absorption fine structure, X-ray photoemission spectra, transport measurement and theoretical calculation. The results provide evidence of three types of coexisting multi-localization transport behaviours in the material; these are heat-carrying phonon-localized resonant scattering, accelerated electron movement and increase in density of states near the Fermi level. The 5p-orbital hybridization between In and Sb is discovered in the In-filled CoSb₃ compound, which results in a charge transfer from Sb to In and the enhancement of p–d orbital hybridization between Co and Sb. Our work demonstrates that the electrical and thermal properties of filled skutterudite bulk thermoelectric materials can be simultaneously optimized through the three types of coexisting multi-localization transport behaviours in an independent way.