Plasticity in single-crystalline Mg₃Bi₂ thermoelectric material

Area of Science:

• Materials Science
• Solid-State Physics
• Crystallography

Background:

• State-of-the-art thermoelectric materials are typically inorganic semiconductors with limited plasticity.
• Directional covalent bonding in these materials restricts tensile strain, often below 5% at room temperature.

Purpose of the Study:

• To investigate the plastic deformation mechanisms and thermoelectric properties of single-crystalline magnesium bismuthide (Mg3Bi2).
• To explore the potential of Mg3Bi2 as a ductile thermoelectric material.

Main Methods:

• Experimental characterization of plastic deformation using slip band and dislocation identification.
• Analysis of chemical bonding to determine slipping barrier energies.
• Measurement of thermoelectric power factor and figure of merit on tellurium-doped Mg3Bi2.

Main Results:

• Single-crystalline Mg3Bi2 demonstrates an unprecedented room-temperature tensile strain of up to 100% along the (0001) plane (ab plane).
• Microscopic analysis revealed dislocation gliding as the primary mechanism for plastic deformation, facilitated by multiple low-barrier slip systems.
• Continuous dynamic bonding prevented atomic plane cleavage, enabling large plastic deformation.
• Tellurium-doped Mg3Bi2 achieved a power factor of ~55 μW/cm/K² and a figure of merit of ~0.65 at room temperature along the ab plane.

Conclusions:

• Mg3Bi2 exhibits exceptional room-temperature ductility, significantly exceeding traditional thermoelectric materials and some metals.
• The unique bonding and slip systems in Mg3Bi2 are responsible for its remarkable plastic deformation capabilities.
• Mg3Bi2 presents a promising candidate for next-generation ductile thermoelectric generators and cooling devices.