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High-Performance GeTe Thermoelectrics in Both Rhombohedral and Cubic Phases
Juan Li1, Xinyue Zhang1, Xiao Wang1
1Interdisciplinary Materials Research Center, School of Materials Science and Engineering , Tongji University , Shanghai 201804 , China.
Journal of the American Chemical Society
|October 27, 2018
Summary
Antimony doping in Germanium Telluride (GeTe) optimizes thermoelectric performance by enhancing band degeneracy and reducing thermal conductivity. This research achieves a high thermoelectric figure of merit (zT) over 2 in both cubic and rhombohedral GeTe phases.
Area of Science:
- Materials Science
- Solid-State Physics
- Thermoelectric Materials
Background:
- Germanium Telluride (GeTe) exhibits phase transitions between cubic and rhombohedral structures.
- Cubic GeTe and related IV-VI semiconductors possess a two-valence-band structure (L and Σ bands) beneficial for thermoelectric performance due to high band degeneracy.
- Rhombohedral GeTe shows altered band ordering and splitting, offering new avenues for manipulating band degeneracy.
Purpose of the Study:
- To optimize carrier concentration and manipulate lattice distortion in GeTe using antimony (Sb) doping.
- To maximize band degeneracy and enhance the electronic performance of GeTe-based thermoelectrics.
- To reduce lattice thermal conductivity through Sb-doping induced phonon scattering.
Main Methods:
- Antimony (Sb) doping of Germanium Telluride (GeTe).
- Investigation of carrier concentration and rhombohedral lattice distortion.
- Analysis of band structure manipulation and phonon scattering mechanisms.
Main Results:
- Sb-doping successfully optimized carrier concentration and controlled rhombohedral lattice distortion.
- Sb-doping enhanced band degeneracy and promoted PbTe solubility, leading to increased phonon scattering by Ge/Pb substitutional defects.
- A superior thermoelectric figure of merit (zT) exceeding 2 was achieved in both rhombohedral and cubic GeTe phases at temperatures below 800 K.
Conclusions:
- Sb-doped GeTe alloys demonstrate excellent thermoelectric properties, positioning them as leading candidates for applications below 800 K.
- The study highlights the critical role of manipulating crystal structure symmetry in advancing thermoelectric materials.
- This work provides a pathway for designing high-performance thermoelectrics through controlled doping and structural modifications.
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