Strong Phonon-Phonon Interactions Securing Extraordinary Thermoelectric Ge1- xSbxTe with Zn-Alloying-Induced Band Alignment

Min Hong, Yuan Wang, Tianli Feng, Qiang Sun, Shengduo Xu, Syo Matsumura, Sokrates T. Pantelides, Jin Zou, Zhi Gang Chen

Research output: Contribution to journalArticle

38 Citations (Scopus)

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 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.

Original languageEnglish
Pages (from-to)1742-1748
Number of pages7
JournalJournal of the American Chemical Society
Volume141
Issue number4
DOIs
Publication statusPublished - Jan 30 2019

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All Science Journal Classification (ASJC) codes

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry

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