Bi-Deficiency Leading to High-Performance in Mg (Sb,Bi) -Based Thermoelectric Materials.

Mg (Sb,Bi) is a potential nearly-room temperature thermoelectric compound composed of earth-abundant elements. However, complex defect tuning and exceptional microstructural control are required. Prior studies have confirmed the detrimental effect of Mg vacancies (V ) in Mg (Sb,Bi) . This study proposes an approach to mitigating the negative scattering effect of V by Bi deficiency, synergistically modulating the electrical and thermal transport properties to enhance the thermoelectric performance. Positron annihilation spectrometry and C -corrected scanning transmission electron microscopy analyses indicated that the V tends to coalesce due to the introduced Bi vacancies (V ). The defects created by Bi deficiency effectively weaken the scattering of electrons from the intrinsic V and enhance phonon scattering. A peak zT of 1.82 at 773 K and high conversion efficiency of 11.3% at ∆T = 473 K are achieved in the optimized composition of Mg (Sb,Bi) by tuning the defect combination. This work demonstrates a feasible and effective approach to improving the performance of Mg (Sb,Bi) as an emerging thermoelectric material.