Tailoring Point Defects to Enhance Thermoelectric Performance in AgCuTe-Based Compounds.

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Low lattice thermal conductivity is crucial for high-performance thermoelectric materials.
• Silver copper telluride (AgCuTe), a superionic conductor, shows promise for medium-temperature thermoelectrics due to its tunable electronic and phononic properties.
• Current AgCuTe applications are limited by suboptimal performance and lack of optimization strategies.

Purpose of the Study:

• To enhance the thermoelectric performance of p-type polycrystalline AgCuTe.
• To explore the efficacy of point defect engineering in optimizing AgCuTe.
• To investigate the synergistic effects of sulfur doping and cation vacancies on thermoelectric properties.

Main Methods:

• Systematic point defect engineering strategy.
• Sulfur doping guided by mass and strain field fluctuation criteria to reduce lattice thermal conductivity.
• Introduction of cation vacancies to further optimize electronic and thermal transport.

Main Results:

• Achieved a dimensionless figure of merit (ZT) of ~1.72 at 773 K in p-type AgCuTe.
• Demonstrated a high average ZT of 1.55 between 523-773 K, surpassing previous AgCuTe records.
• Developed a segmented thermoelectric module with ~13.7% energy conversion efficiency using optimized AgCuTe.

Conclusions:

• Point defect engineering is an effective strategy for optimizing superionic conductors like AgCuTe.
• Optimized AgCuTe shows significant potential for practical medium-temperature thermoelectric applications.
• The study provides a pathway for developing advanced thermoelectric materials through defect control.