Strong phonon–phonon interactions securing extraordinary thermoelectric Ge1–xSbxTe with Zn-alloying-induced band alignment

Hong, Min and Wang, Yuan and Feng, Tianli and Sun, Qiang and Xu, Shengduo and Matsumura, Syo and Pantelides, Sokrates T. and Zou, Jin and Chen, Zhi-Gang (2019) Strong phonon–phonon interactions securing extraordinary thermoelectric Ge1–xSbxTe with Zn-alloying-induced band alignment. Journal of the American Chemical Society, 141 (4). pp. 1742-1748.

Abstract

The ability of substitution atoms to decrease thermal conductivity is usually ascribed to the enhanced phonon-impurity scattering by assuming the original phonon dispersion relations. In this study, we find that 10% SbGe alloying in GeTe modifies the phonon dispersions significantly, closes the acoustic–optical phonon band gap, increases the phonon–phonon scattering rates, and reduces the phonon group velocities. These changes, together with grain boundaries, nanoprecipitates, and planar vacancies, lead to a significant decrease in the lattice thermal conductivity. In addition, an extra 2–6% Zn alloying decreases the energy offset between valence band edges at L and Σ points in Ge1–xSbxTe that is found to be induced by the Ge 4s2 lone pairs. Since Zn is free of s2 lone pair electrons, substituting Ge with Zn atoms can consequently diminish the Ge 4s2 lone-pair characters and reduce the energy offset, resulting in two energetically merged valence band maxima. The refined band structures render a power factor up to 40 μW cm–1 K–2 in Ge0.86Sb0.1Zn0.04Te. Ultimately, a superhigh zT of 2.2 is achieved. This study clarifies the impacts of high-concentration substitutional atoms on phonon band structure, phonon–phonon scattering rates, and the convergence of electron valence band edges, which could provide guidelines for developing high-performance thermoelectric materials.


Statistics for USQ ePrint 35501
Statistics for this ePrint Item
Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Published version cannot be displayed due to copyright restrictions.
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Faculty/School / Institute/Centre: Current - Institute for Advanced Engineering and Space Sciences - Centre for Future Materials (1 Jan 2017 -)
Date Deposited: 09 Oct 2019 05:04
Last Modified: 09 Oct 2019 05:17
Uncontrolled Keywords: high-performance; progress; figure; merit; SNTE
Fields of Research : 09 Engineering > 0912 Materials Engineering > 091205 Functional Materials
Funding Details:
Identification Number or DOI: 10.1021/jacs.8b12624
URI: http://eprints.usq.edu.au/id/eprint/35501

Actions (login required)

View Item Archive Repository Staff Only