Ultralow Lattice Thermal Conductivity and Enhanced Mechanical Properties of Cu and Sb Co-Doped SnTe Thermoelectric Material with a Complex Microstructure Evolution

Abstract

SnTe is an exceptionally promising eco-friendly thermoelectric material that continues to draw immense interest as a source of alternative energy recovered from waste heat energy. Here, we investigate the effect of introducing Cu as a single doping element rather than phase separated in SnTe followed by Sb co-doping to tune the lattice thermal conductivity. A microstructure evolution was observed which influences the thermoelectric performance of these SnTe-based materials. An overall power factor of ∼22 μW/cmK2 and an ultralow lattice thermal conductivity of 0.39 W/mK are reported. A maximum ZT of 0.86 is also reported with an all-time record high hardness value of 165 Hv among SnTe-based thermoelectric materials. Through DFT calculations, we show that Cu opens the band gap of SnTe, whereas Sb in the presence of Cu introduces resonance levels and causes band convergence. This kind of enhanced thermoelectric performance is paramount for the application of SnTe in recovery of heat into useful electrical energy.