Vacancy driven microstructural induced thermoelectric performance in GeTe based compounds
Khasim saheb Bayikadi1*, Chien Ting Wu4, Li-Chyong Chen3, Kuei-Hsien Chen2, Fang-Cheng Chou3, Sankar Raman1
1Institute of Physics, Academia Sinica, Taipei, Taiwan
2Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, Taiwan
3Center for condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
4Taiwan Semiconductor Research Institute, TSMC, Hsinchu, Taiwan
* Presenter:Khasim saheb Bayikadi,
In addition to the Ge-vacancy control of GeTe, the antimony (Sb) substitution of GeTe for the improvement of thermoelectric performance is explored for Ge0.9Sb0.1Te. The concomitant carrier concentration (n) and the aliovalent Sb ion substitution led to an optimal doping level of x = 0.10 to show ZT ~ 2.35 near 800 K, which is significantly higher than those single- and multi-element substitution studies of the GeTe system reported in the literature. In addition, Ge0.9Sb0.1Te demonstrates an impressively high power factor of 36 mW cm-1 K-2 and a low thermal conductivity of 1.1 W m-1 K-1 at 800 K. The enhanced ZT level for Ge0.9Sb0.1Te is explained through a systematic investigation of micro-structural change and strain analysis from room temperature to 800 K. A significant reduction of lattice thermal conductivity (klat) is identified and explained by the Sb substitution-introduced strained and widened domain boundaries for the herringbone domain structure of Ge0.9Sb0.1Te. The Sb substitution created multiple forms of strain near the defect centre, the herringbone domain structure, and widened tensile/compressive domain boundaries to support phonon scattering that covers a wide frequency range of the phonon spectrum to reduce lattice thermal conductivity effectively.

Keywords: GeTe, Microdomains, herringbone structure, strain, thermoelectric performance