Synergistic Microstructure and Composition Engineering via Na₂S Enables High-Performance Porous PbTe Thermoelectrics...

Area of Science:

• Materials Science
• Solid-State Physics
• Sustainable Energy

Background:

• Thermoelectric (TE) materials convert heat to electricity but face challenges in optimizing transport properties.
• Simultaneous enhancement of electrical and thermal transport is crucial for practical TE applications.

Purpose of the Study:

• To develop a co-design strategy for PbTe-based TE materials using Na2S-assisted synthesis.
• To achieve high thermoelectric performance through microstructural and compositional engineering.

Main Methods:

• Solid-state synthesis of PbTe with Na2S to create hierarchical porosity and Na doping.
• Microstructural characterization to analyze grain refinement, nanoprecipitates, and dislocations.
• Evaluation of thermal conductivity, electrical transport, and TE figure of merit (zT).

Main Results:

• Optimized composition (Pb0.97Na0.03Te-1.0%Na2S) achieved ultralow lattice thermal conductivity (≈0.50 W m⁻¹ K⁻¹ at 750 K).
• Peak TE figure of merit (zT) of ≈2.2 at 823 K and average zT ≈1.9 from 623-823 K.
• Single-leg TE modules demonstrated 13.4% conversion efficiency; unicouple modules reached 2.2 W cm⁻² power density.

Conclusions:

• Na2S-assisted synthesis enables concurrent optimization of phonon scattering, carrier concentration, and band convergence in PbTe.
• The developed strategy offers a scalable pathway for advancing mid-temperature TE materials and devices.
• High device performance validates the potential of engineered PbTe for efficient heat-to-electricity conversion.