Bi-Deficiency Leading to High-Performance in Mg3(Sb,Bi)2-Based Thermoelectric Materials

Mg-3(Sb,Bi)(2) 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-Mg) in Mg-3(Sb,Bi)(2). This study proposes an approach to mitigating the negative scattering effect of V-Mg by Bi deficiency, synergistically modulating the electrical and thermal transport properties to enhance the thermoelectric performance. Positron annihilation spectrometry and C-s-corrected scanning transmission electron microscopy analyses indicated that the V-Mg tends to coalesce due to the introduced Bi vacancies (V-Bi). The defects created by Bi deficiency effectively weaken the scattering of electrons from the intrinsic V-Mg and enhance phonon scattering. A peak zT of 1.82 at 773 K and high conversion efficiency of 11.3% at increment T = 473 K are achieved in the optimized composition of Mg-3(Sb,Bi)(2) by tuning the defect combination. This work demonstrates a feasible and effective approach to improving the performance of Mg-3(Sb,Bi)(2) as an emerging thermoelectric material.

Automated summary

This study proposes an approach to enhance the thermoelectric performance of Mg-3(Sb,Bi)(2) by mitigating the negative effect of Mg vacancies through Bi deficiency. By tuning the defect combination, the optimized composition achieved a peak zT of 1.82 at 773 K and a high conversion efficiency of 11.3% at an increment T = 473 K.