Improved thermoelectric performance by microwave wet chemical synthesis of low thermal conductivity SnTe

Abstract

SnTe is a promising replacement for PbTe due to its non-toxicity and high thermoelectric conversion efficiency. However, it suffers from poor performance caused by the presence of tin vacancies and a wide energy gap between the light and heavy valence bands, as well as high thermal conductivity that inhibits its thermoelectric properties. In this work, complexes of in situ grown SnTe with Bi doping were synthesized by microwave wet chemical synthesis. The complex morphology of the micro-nanoparticles and the formation of holes after spark plasma sintering suppress phonon scattering and greatly reduce the lattice thermal conductivity of the system. The band structure and phonon dispersion of Bi doped SnTe were calculated by first principles, and the reasons for the improvement of electric transport properties and the decrease of thermal conductivity of SnTe were investigated, combined with mechanical properties and sound speed reduction. The effects of various mechanisms such as polycrystalline interfaces, point defects, complex morphologies, and phonon dispersion flat bands on phonon scattering are discussed in detail and the obtaining mechanism of low lattice thermal conductivity is understood.