Compositional Fluctuations Locked by Athermal Transformation Yielding High Thermoelectric Performance in GeTe

Area of Science:

• Materials Science
• Solid State Physics
• Thermodynamics

Background:

• Phase transitions in thermoelectric (TE) materials present challenges for device operation but offer opportunities near electronic instabilities.
• Controlling these phase transitions is key to optimizing TE material properties.

Purpose of the Study:

• To investigate the effects of Sb doping on GeTe phase transitions and thermoelectric properties.
• To explore a new thermodynamic route for enhancing TE material performance.

Main Methods:

• Utilizing Sb doping to induce spontaneous composition fluctuations and uphill diffusion in GeTe.
• Analyzing the interplay between diffusionless athermal cubic-to-rhombohedral phase transition and Sb-induced fluctuations.
• Alloying GeTe with Sb2Te3 to modify microstructure and suppress thermal conductivity.

Main Results:

• Sb doping elicits composition fluctuations and phase coexistence (cubic and rhombohedral) in GeTe.
• Alloying with Sb2Te3 significantly reduces thermal conductivity while maintaining optimal carrier concentration.
• Achieved exceptional figures-of-merit (zT) greater than 2.6 over a wide composition range.

Conclusions:

• Phase transition manipulation via Sb doping is effective in optimizing GeTe microstructure for enhanced TE performance.
• The study demonstrates a novel thermodynamic approach to developing high-performance thermoelectric materials.
• These findings open new avenues for designing advanced TE devices.