Enhancing Thermoelectric Performance of AgSbTe₂-Based Compounds via Microstructure Modulation Combining with Entropy...

Area of Science:

• Materials Science
• Solid State Physics
• Thermoelectrics

Background:

• Thermoelectric materials convert heat to electricity, crucial for waste heat recovery.
• Improving thermoelectric performance relies on microstructure and configurational entropy.
• The interplay between synthesis, structure, and thermoelectric properties requires further clarification.

Purpose of the Study:

• To investigate the correlation between preparation methods, microstructure, configurational entropy, and thermoelectric properties in AgSbTe2-based compounds.
• To compare the effects of equilibrium melting-slow cooling versus nonequilibrium melting-quenching-spark plasma sintering (SPS) methods.
• To optimize thermoelectric performance through controlled synthesis and composition tuning.

Main Methods:

• Synthesis of AgSbTe2-based compounds using equilibrium melting-slow cooling and nonequilibrium melting-quenching-SPS methods.
• Characterization of microstructure, including grain size and defect concentration.
• Evaluation of thermoelectric properties: carrier mobility, carrier concentration, thermal conductivity, and figure of merit (ZT).

Main Results:

• Equilibrium method yielded larger grains (>300 μm) and lower defect concentration, resulting in significantly higher carrier mobility (10.66 cm2 V-1 s-1) compared to the nonequilibrium method (1.83 cm2 V-1 s-1).
• Tuning nonstoichiometric AgSbTe2 composition enhanced configurational entropy and created cation vacancies, leading to dense dislocations.
• Ultralow thermal conductivity (0.51 W m-1 K-1) at room temperature was achieved for the equilibrium-synthesized (Ag2Te)0.42(Sb2Te3)0.58 sample.
• The (Ag2Te)0.42(Sb2Te3)0.58 sample from equilibrium synthesis exhibited the highest ZT of 1.04 at 500 K, a >60% improvement over the nonequilibrium counterpart.

Conclusions:

• The equilibrium melting-slow cooling method is superior for enhancing thermoelectric performance in AgSbTe2-based materials.
• Microstructure control, configurational entropy, and defect engineering are key strategies for optimizing thermoelectric properties.
• This study provides a pathway for designing high-performance thermoelectric materials through careful selection of synthesis routes and composition.