Lattice Regularization by Manipulating Over-Stoichiometric Defects Yields High-Performance (Bi,Sb)₂Te₃...

Area of Science:

• Materials Science
• Condensed Matter Physics
• Nanotechnology

Background:

• Bismuth telluride (Bi2Te3)-based alloys are crucial for near-ambient-temperature thermoelectric technology.
• Intrinsic defects in Bi2Te3 alloys, such as "donor-like" effects, significantly impair transport properties.
• Optimizing thermoelectric performance requires addressing these defect-related limitations.

Purpose of the Study:

• To mitigate the negative impact of intrinsic defects in Bi2-xSbxTe3 alloys.
• To enhance carrier mobility and thermoelectric transport properties.
• To improve the overall efficiency of Bi2Te3-based thermoelectric power generators.

Main Methods:

• Controlled addition of over-stoichiometric antimony (Sb) to fill tellurium (Te) vacancies.
• Introduction of boost-generated antisite defects to compensate for charge carriers.
• Dilute copper (Cu) doping to promote microstructural modulation, including Sb nanoprecipitates and twins.

Main Results:

• Reduced defect scattering and enhanced carrier mobility due to Sb filling Te vacancies.
• Improved thermoelectric figure of merit (ZT) with a peak of ≈1.50 at 350 K and an average of 1.25 from 300 to 500 K.
• Development of 17-pair power generators achieving 6.7% conversion efficiency under a 200 K temperature gradient.

Conclusions:

• Strategic control of stoichiometry and doping in Bi2Te3 alloys effectively decouples electrical and thermal transport.
• The optimized materials demonstrate superior thermoelectric performance and stability.
• These findings present a promising pathway for advancing Bi2Te3-based generators in low-grade waste heat recovery applications.