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

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Mg3(Sb,Bi)2 is a promising thermoelectric material using earth-abundant elements for near-room temperature applications.
• Effective thermoelectric performance requires precise control over complex defects and microstructure.
• Magnesium vacancies (VMg) in Mg3(Sb,Bi)2 have been shown to negatively impact thermoelectric properties.

Purpose of the Study:

• To mitigate the detrimental electron scattering effect of Mg vacancies (VMg).
• To synergistically modulate electrical and thermal transport properties through Bi deficiency.
• To enhance the overall thermoelectric performance of Mg3(Sb,Bi)2.

Main Methods:

• Introduced bismuth vacancies (VBi) into the Mg3(Sb,Bi)2 structure.
• Utilized positron annihilation spectrometry to analyze defect behavior.
• Employed Cs-corrected scanning transmission electron microscopy for microstructural investigation.

Main Results:

• Bi deficiency induced VMg coalescence, weakening electron scattering from intrinsic VMg.
• Enhanced phonon scattering was observed due to the introduced defects.
• Achieved a peak thermoelectric figure of merit (zT) of 1.82 at 773 K and 11.3% conversion efficiency.

Conclusions:

• Tuning the defect combination, specifically by introducing Bi deficiency, is an effective strategy.
• This approach successfully mitigates negative scattering effects and enhances thermoelectric performance.
• Demonstrates a feasible method for improving Mg3(Sb,Bi)2 as an emerging thermoelectric material.