Interface kinetic manipulation enabling efficient and reliable Mg₃Sb₂ thermoelectrics

Area of Science:

• Materials Science
• Energy Conversion
• Solid State Physics

Background:

• Thermoelectric generators (TEGs) are crucial for sustainable energy, but interfacial issues between materials and electrodes limit their efficiency and reliability.
• Current methods for creating barrier layers often overlook the kinetics of interfacial reactions and diffusion, relying instead on thermodynamic equilibrium.
• Effective barrier layers are needed to mitigate losses and prevent failures in thermoelectric devices.

Purpose of the Study:

• To develop a novel interfacial barrier layer for magnesium antimonide (Mg₃Sb₂)-based thermoelectric materials.
• To address the limitations of existing barrier layer approaches by considering reaction and diffusion kinetics.
• To enhance the efficiency and long-term stability of thermoelectric generators for waste heat recovery.

Main Methods:

• Utilized titanium (Ti) foil as a barrier layer for Mg₃Sb₂ thermoelectric materials.
• Investigated the distinct chemical reaction activities and diffusion behaviors of Ti during sintering and device operation.
• Characterized the interfacial contact resistivity and evaluated the performance and durability of the resulting thermoelectric modules.

Main Results:

• A highly reactive ternary MgTiSb metastable phase formed during sintering, transforming into stable binary Ti-Sb alloys during operation.
• Achieved a low interfacial contact resistivity below 5 μΩ·cm².
• Demonstrated a Mg₃Sb₂-based module efficiency of up to 11% at a temperature difference of 440 K, surpassing state-of-the-art medium-temperature modules.
• Exhibited negligible degradation in Ti foil/Mg₃(Sb,Bi)₂ joints over long-term thermal cycling.

Conclusions:

• Titanium foil serves as an effective and robust barrier layer for Mg₃Sb₂-based thermoelectric materials, overcoming limitations of previous methods.
• The developed interfaces enable high module efficiency and excellent long-term stability, crucial for practical thermoelectric applications.
• This approach paves the way for efficient and sustainable waste heat recovery systems.