AgCl Addition to Chalcopyrite Compound for Ultra-Low Thermal Conductivity in Realizing High ZT Thermoelectric...

Area of Science:

• Materials Science
• Solid State Physics
• Thermoelectrics

Background:

• Thermoelectric materials are crucial for energy conversion, but their efficiency is limited by high thermal conductivity.
• Cu2GaTe2 exhibits promising thermoelectric properties but suffers from high intrinsic thermal conductivity, hindering performance.
• Reducing lattice thermal conductivity is key to optimizing thermoelectric materials.

Purpose of the Study:

• To investigate the effect of AgCl addition on the thermal conductivity of Cu2GaTe2.
• To explore methods for reducing lattice thermal conductivity while preserving electrical properties in Cu2GaTe2.
• To enhance the overall thermoelectric figure of merit (ZT) of Cu2GaTe2.

Main Methods:

• Solid-phase melting method was used to introduce AgCl into the Cu2GaTe2 matrix.
• Experimental measurements of thermal and electrical properties were conducted.
• First-principles calculations were employed to understand the underlying mechanisms of thermal conductivity reduction.

Main Results:

• AgCl addition led to multiple scattering mechanisms, significantly reducing lattice thermal conductivity.
• First-principles calculations confirmed that Ag doping decreases elastic constants and sound velocity, contributing to lower thermal conductivity.
• Hole formation due to Cl escape during sintering further enhanced phonon scattering and reduced thermal conductivity.
• The (Cu2GaTe2)0.96(AgCl)0.04 sample achieved an ultra-high ZT value of 1.4 at 823 K without compromising electrical performance.

Conclusions:

• Introduction of AgCl effectively reduces the thermal conductivity of Cu2GaTe2 through phonon scattering.
• The strategy of incorporating AgCl is a viable approach to enhance thermoelectric performance.
• The optimized (Cu2GaTe2)0.96(AgCl)0.04 sample demonstrates excellent potential for thermoelectric applications.