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

Yi-Fen Tsai; Pai-Chun Wei; Liuwen Chang; Kuang-Kuo Wang; Chun-Chuen Yang; Yen-Chung Lai; Cheng-Rong Hsing; Ching-Ming Wei; Jian He; G Jeffrey Snyder; Hsin-Jay Wu

doi:10.1002/adma.202005612

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

Adv Mater. 2021 Jan;33(1):e2005612. doi: 10.1002/adma.202005612. Epub 2020 Nov 20.

Authors

Yi-Fen Tsai^{1

2}, Pai-Chun Wei^{3

4}, Liuwen Chang¹, Kuang-Kuo Wang¹, Chun-Chuen Yang⁵, Yen-Chung Lai⁶, Cheng-Rong Hsing⁷, Ching-Ming Wei⁷, Jian He⁸, G Jeffrey Snyder⁹, Hsin-Jay Wu²

Affiliations

¹ Department of Materials and Optoelectronic science, National Sun Yat-sen University, Kaohsiung, 80424, Taiwan.
² Department of Materials Science and Engineering, National Chiao Tung University, Hsinchu, 30010, Taiwan.
³ Computer, Electrical, and Mathematical Sciences and Engineering Division, King Abdullah University of Science and Technology (KAUST), Thuwal, 23955-6900, Saudi Arabia.
⁴ Center for Condensed Matter Sciences and Center of Atomic Initiative for New Materials, National Taiwan University, Taipei, 10617, Taiwan.
⁵ Department of Physics, Chung Yuan Christian University, Chung-Li, Jhongli, 32023, Taiwan.
⁶ National Synchrotron Radiation Research Center, Hsinchu, 30076, Taiwan.
⁷ Institute of Atomic and Molecular Sciences, Academia Sinica, Taipei, 10617, Taiwan.
⁸ Department of Physics and Astronomy, Clemson Nanomaterials Institute, Clemson University, Clemson, 29634-0978, USA.
⁹ Department of Materials Science and Engineering, Northwestern University, Evanston, IL, 60208, USA.

PMID: 33215757
DOI: 10.1002/adma.202005612

Abstract

Phase transition in thermoelectric (TE) material is a double-edged sword-it is undesired for device operation in applications, but the fluctuations near an electronic instability are favorable. Here, Sb doping is used to elicit a spontaneous composition fluctuation showing uphill diffusion in GeTe that is otherwise suspended by diffusionless athermal cubic-to-rhombohedral phase transition at around 700 K. The interplay between these two phase transitions yields exquisite composition fluctuations and a coexistence of cubic and rhombohedral phases in favor of exceptional figures-of-merit zT. Specifically, alloying GeTe by Sb₂ Te₃ significantly suppresses the thermal conductivity while retaining eligible carrier concentration over a wide composition range, resulting in high zT values of >2.6. These results not only attest to the efficacy of using phase transition in manipulating the microstructures of GeTe-based materials but also open up a new thermodynamic route to develop higher performance TE materials in general.

Keywords: displacive phase transformation; germanium telluride; thermoelectric figure of merit.

Grants and funding

108-2636-E-110-001/Young Scholar Fellowship Program by Ministry of Science and Technology