Grain Boundary Strengthening Achieves Extraordinary Module Efficiency in GeTe-Based Thermoelectric Materials

Area of Science:

• Materials Science
• Solid State Physics
• Nanotechnology

Background:

• Planar defects like grain boundaries significantly affect phonon and carrier transport in Germanium Telluride (GeTe) thermoelectric materials.
• Achieving high thermoelectric figure of merit (zT) and mechanical robustness simultaneously in GeTe is challenging.

Purpose of the Study:

• To simultaneously enhance the thermoelectric figure of merit (zT) and mechanical strength of highly alloyed GeTe.
• To investigate the impact of Cd doping and Cu2Se-PbSe co-alloying on GeTe's thermoelectric and mechanical properties.

Main Methods:

• Cd doping and Cu2Se-PbSe co-alloying of GeTe.
• Formation of dense nano-grain boundaries and point defects to scatter phonons.
• Optimization of carrier concentration and valence band convergence for improved electronic transport.

Main Results:

• Achieved a peak zT of 2.1 at 700 K and an average zT of 1.4 (300-800 K) in (Ge0.98Cd0.02Te)0.88(Cu2Se)0.02(PbSe)0.1.
• Obtained high Vickers hardness of approximately 210 HV due to hierarchical structures.
• Fabricated a thermoelectric module with 0.86 W cm-2 output power density and 11% conversion efficiency at ΔT = 501 K.

Conclusions:

• Simultaneous optimization of phonon scattering and electronic transport leads to superior thermoelectric performance in alloyed GeTe.
• The developed GeTe material exhibits excellent mechanical strength, crucial for practical thermoelectric device applications.
• The synergistic improvements in zT and mechanical properties enable high-efficiency thermoelectric energy conversion.