Balancing electron and phonon scatterings while tailoring carrier concentration in SnTe for enhancing thermoelectric performance

Balancing electron and phonon scattering is crucial for enhancing the thermoelectric (TE) performance of materials. Herein, the TE performance of Mg-alloyed SnTe was significantly enhanced by managing lattice defects. Formation of Sn vacancies in Mg-alloyed SnTe was suppressed via Sn-compensation, leading to 23% higher carrier mobility and 29% higher power factor (PF) of SnMgTe than those of SnBiMgTe with Bi-doping. Transmission electron microscopy analysis confirmed the formation of dense dislocation arrays in SnBiMgTe, resulting in an ultra-low lattice thermal conductivity (κ = 0.34 W mK) at 823 K. A combination of Sn-compensation and Bi-doping in SnBiMgTe resulted in high PF and low κ, simultaneously, owing to the balanced scatterings of electron and phonon. Furthermore, carrier concentration was optimised, with a high figure of merit (ZT ∼1.3) achieved at 873 K, ∼50% higher than that obtained by applying either Sn-compensation or Bi-doping individually.