Thermoelectric Transport Performance in p-Type AgSbTe₂-Based Materials through Entropy Engineering.

Area of Science:

• Materials Science
• Solid-State Physics
• Thermoelectrics

Background:

• Silver antimony telluride (AgSbTe2) based materials are promising for thermoelectric applications.
• The presence of Ag2Te impurity phases hinders their thermoelectric performance.
• Understanding and controlling phase transitions near 425 K is crucial for optimizing properties.

Purpose of the Study:

• To stabilize AgSbTe2 and improve its thermoelectric performance through Sn/Ge alloying.
• To investigate the effect of Sn/Ge addition on the solubility limit and suppression of Ag2Te.
• To explore the high-entropy effect on the crystal structure and transport properties.

Main Methods:

• Synthesis of AgSbTe2 compounds with Sn/Ge alloying using melting, annealing, and hot pressing.
• Characterization of structural, electrical, and thermal transport properties.
• Density functional theory (DFT) calculations to understand electronic band structure and defect behavior.

Main Results:

• Sn/Ge alloying extended the solubility limit in AgSbTe2 up to ~30%, effectively suppressing Ag2Te.
• A high-entropy Ag0.85Sn0.15Sb0.85Ge0.15Te2 compound exhibited a stabilized rock-salt structure.
• A high power factor of ~10.8 μW cm⁻¹ K⁻² was achieved at 757 K due to multivalence bands and reduced energy offsets.
• Lattice thermal conductivity decreased due to entropy-induced defects, leading to a figure of merit of ~1.5 at 757 K.

Conclusions:

• Sn/Ge alloying is an effective strategy to stabilize AgSbTe2 and enhance thermoelectric performance.
• The high-entropy approach can inhibit impurity phases and extend solubility limits in thermoelectric materials.
• This study provides a roadmap for optimizing group IV-VI materials for high thermoelectric efficiency.