High Ductility and Excellent Thermoelectric Performance in Te-Stabilized Cubic Ag₂TeS_1- Solid Solutions

Area of Science:

• Materials Science
• Solid-State Chemistry
• Thermoelectrics

Background:

• The cubic phase of silver sulfide (Ag₂S) is desirable for thermoelectric applications but is unstable at low temperatures.
• Phase transitions in Ag₂S lead to detrimental changes in mechanical and thermoelectric properties.
• Developing materials that stabilize the cubic phase is key to improving thermoelectric device reliability.

Purpose of the Study:

• To investigate the stabilization of the Ag₂S cubic phase using silver telluride (Ag₂Te) doping.
• To evaluate the mechanical behavior and thermoelectric performance of Ag₂TeₓS₁₋ₓ solid solutions.
• To identify optimal compositions for high-performance, durable thermoelectric materials.

Main Methods:

• Synthesis of Ag₂TeₓS₁₋ₓ solid solutions with varying tellurium content (0.20 ≤ x ≤ 0.30).
• Phase stability analysis across a temperature range of 300 K to 773 K.
• Mechanical testing, including bending tests to assess ductility and yield strength.
• Thermoelectric property measurements, including figure of merit (ZT).

Main Results:

• Ag₂TeₓS₁₋ₓ (0.20 ≤ x ≤ 0.30) samples maintained a stable cubic phase from 300 K to 773 K.
• Samples exhibited superior ductility and no fractures during bending tests, unlike pure Ag₂S.
• The Ag₂Te₀.₂₀S₀.₈₀ sample showed a high bending average yield strength (46.52 MPa at 673 K).
• Thermoelectric performance surpassed InSe and pure Ag₂S, with Ag₂Te₀.₃₀S₀.₇₀ achieving a ZT of 0.59 at 723 K.

Conclusions:

• Doping Ag₂S with Ag₂Te effectively stabilizes the cubic phase, enhancing mechanical robustness.
• The developed Ag₂TeₓS₁₋ₓ solid solutions demonstrate significant potential for durable thermoelectric applications.
• Optimized compositions offer improved thermoelectric efficiency and mechanical integrity compared to existing materials.