High density lath twins lead to high thermoelectric conversion efficiency in Bi₂Te₃ modules

Area of Science:

• Materials Science
• Solid State Physics
• Energy Harvesting

Background:

• Bismuth telluride (Bi2Te3)-based thermoelectric generators are key for low-grade heat harvesting.
• Optimizing thermoelectric performance requires precise control over material microstructure and properties.

Purpose of the Study:

• To develop a combinative doping strategy using Ag and Ga in Ag9GaTe6 to enhance the ZT value of p-type Bi0.4Sb1.6Te3.
• To investigate the impact of this doping on microstructure, thermal conductivity, power factor, and mechanical hardness.

Main Methods:

• A combinative doping strategy with Ag and Ga (in Ag9GaTe6) was applied to p-type Bi0.4Sb1.6Te3.
• Microstructural analysis was performed to identify phonon scattering centers.
• Thermoelectric properties (ZT, power factor, thermal conductivity) and Vickers hardness were measured.

Main Results:

• The doping strategy introduced multiple phonon scattering centers (lath twins, triple junction boundaries, Sb-rich nanoprecipitates), suppressing lattice thermal conductivity to 0.50 W m⁻¹ K⁻¹.
• Enhanced room-temperature power factor to 48.8 μW cm⁻¹ K⁻² and Vickers hardness to 0.90 GPa.
• Achieved a peak ZT of 1.40 at 350 K and an average ZT (ZTave) of 1.24 from 300-500 K.

Conclusions:

• The novel doping approach significantly improves thermoelectric performance and mechanical stability of Bi2Te3-based materials.
• A 17-couple thermoelectric module achieved a 6.5% conversion efficiency at ΔT = 200 K with stable output after 30 thermal cycles.
• This work demonstrates a promising strategy for efficient and durable thermoelectric energy harvesting devices.