Local reaction-global diffusion unlocks high-performance Mg₃(Sb,Bi)₂-based thermoelectrics

Area of Science:

• Materials Science
• Solid State Physics
• Energy Conversion

Background:

• Mg3(Sb,Bi)2-based thermoelectrics (TEs) are promising for near-room-temperature applications.
• Improving their electrical power factors and figures-of-merit (zTs) is limited by Mg-vacancy control and understanding underlying mechanisms.

Purpose of the Study:

• To develop a novel in-situ Mg-vacancy engineering strategy for Mg3(Sb,Bi)2 thermoelectrics.
• To enhance carrier mobility and thermoelectric performance through precise defect control.

Main Methods:

• In-situ Mg-vacancy engineering via local reactions and global diffusion during spark-plasma-sintering.
• Multiscale investigation to elucidate the local-reaction-global-diffusion mechanism.
• Fabrication and testing of thermoelectric modules for power generation and cooling.

Main Results:

• Achieved record-high power factors and figures-of-merit (zTs) in vacancy-restrained Mg3(Sb,Bi)2.
• Demonstrated high-performance thermoelectric generator modules with power densities up to 1.23 W cm⁻² at ΔT = 315 K.
• Peltier modules achieved competitive cooling temperature differences (ΔTmax) exceeding 70 K at 303 K.

Conclusions:

• The developed local-reaction-global-diffusion strategy effectively engineers Mg-vacancies, enhancing thermoelectric properties.
• This approach offers a pathway to optimize other energy materials, TE-interface materials, and metal-semiconductor interfaces.
• The findings pave the way for advanced thermoelectric devices for energy harvesting and cooling applications.