Avoided crossing of rattler modes in thermoelectric materials

Mogens Christensen, Asger Bech Abrahamsen, Niels Bech Christensen, Fanny Juranyi, Niels Hessel Andersen, Kim Lefmann, Jakob Andreasson, Christian Robert Haffenden Bahl, Bo B. Iversen

    Research output: Contribution to journalJournal articleResearchpeer-review

    Abstract

    Engineering of materials with specific physical properties has recently focused on the effect of nano-sized 'guest domains' in a 'host matrix' that enable tuning of electrical, mechanical, photo-optical or thermal properties. A low thermal conductivity is a prerequisite for obtaining effective thermoelectric materials, and the challenge is to limit the conduction of heat by phonons, without simultaneously reducing the charge transport. This is named the 'phonon glass-electron crystal' concept and may be realized in host-guest systems. The guest entities are believed to have independent oscillations, so-called rattler modes, which scatter the acoustic phonons and reduce the thermal conductivity. We have investigated the phonon dispersion relation in the phonon glass-electron crystal material Ba8Ga16Ge30 using neutron triple-axis spectroscopy. The results disclose unambiguously the theoretically predicted avoided crossing of the rattler modes and the acoustic-phonon branches. The observed phonon lifetimes are longer than expected, and a new explanation for the low k(L) is provided.
    Original languageEnglish
    JournalNature Materials
    Volume7
    Issue number10
    Pages (from-to)811-815
    ISSN1476-1122
    DOIs
    Publication statusPublished - 2008

    Cite this

    Christensen, M., Abrahamsen, A. B., Christensen, N. B., Juranyi, F., Andersen, N. H., Lefmann, K., ... Iversen, B. B. (2008). Avoided crossing of rattler modes in thermoelectric materials. Nature Materials, 7(10), 811-815. https://doi.org/10.1038/nmat2273
    Christensen, Mogens ; Abrahamsen, Asger Bech ; Christensen, Niels Bech ; Juranyi, Fanny ; Andersen, Niels Hessel ; Lefmann, Kim ; Andreasson, Jakob ; Bahl, Christian Robert Haffenden ; Iversen, Bo B. / Avoided crossing of rattler modes in thermoelectric materials. In: Nature Materials. 2008 ; Vol. 7, No. 10. pp. 811-815.
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    abstract = "Engineering of materials with specific physical properties has recently focused on the effect of nano-sized 'guest domains' in a 'host matrix' that enable tuning of electrical, mechanical, photo-optical or thermal properties. A low thermal conductivity is a prerequisite for obtaining effective thermoelectric materials, and the challenge is to limit the conduction of heat by phonons, without simultaneously reducing the charge transport. This is named the 'phonon glass-electron crystal' concept and may be realized in host-guest systems. The guest entities are believed to have independent oscillations, so-called rattler modes, which scatter the acoustic phonons and reduce the thermal conductivity. We have investigated the phonon dispersion relation in the phonon glass-electron crystal material Ba8Ga16Ge30 using neutron triple-axis spectroscopy. The results disclose unambiguously the theoretically predicted avoided crossing of the rattler modes and the acoustic-phonon branches. The observed phonon lifetimes are longer than expected, and a new explanation for the low k(L) is provided.",
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    author = "Mogens Christensen and Abrahamsen, {Asger Bech} and Christensen, {Niels Bech} and Fanny Juranyi and Andersen, {Niels Hessel} and Kim Lefmann and Jakob Andreasson and Bahl, {Christian Robert Haffenden} and Iversen, {Bo B.}",
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    Christensen, M, Abrahamsen, AB, Christensen, NB, Juranyi, F, Andersen, NH, Lefmann, K, Andreasson, J, Bahl, CRH & Iversen, BB 2008, 'Avoided crossing of rattler modes in thermoelectric materials', Nature Materials, vol. 7, no. 10, pp. 811-815. https://doi.org/10.1038/nmat2273

    Avoided crossing of rattler modes in thermoelectric materials. / Christensen, Mogens; Abrahamsen, Asger Bech; Christensen, Niels Bech; Juranyi, Fanny; Andersen, Niels Hessel; Lefmann, Kim; Andreasson, Jakob; Bahl, Christian Robert Haffenden; Iversen, Bo B.

    In: Nature Materials, Vol. 7, No. 10, 2008, p. 811-815.

    Research output: Contribution to journalJournal articleResearchpeer-review

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    T1 - Avoided crossing of rattler modes in thermoelectric materials

    AU - Christensen, Mogens

    AU - Abrahamsen, Asger Bech

    AU - Christensen, Niels Bech

    AU - Juranyi, Fanny

    AU - Andersen, Niels Hessel

    AU - Lefmann, Kim

    AU - Andreasson, Jakob

    AU - Bahl, Christian Robert Haffenden

    AU - Iversen, Bo B.

    PY - 2008

    Y1 - 2008

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    AB - Engineering of materials with specific physical properties has recently focused on the effect of nano-sized 'guest domains' in a 'host matrix' that enable tuning of electrical, mechanical, photo-optical or thermal properties. A low thermal conductivity is a prerequisite for obtaining effective thermoelectric materials, and the challenge is to limit the conduction of heat by phonons, without simultaneously reducing the charge transport. This is named the 'phonon glass-electron crystal' concept and may be realized in host-guest systems. The guest entities are believed to have independent oscillations, so-called rattler modes, which scatter the acoustic phonons and reduce the thermal conductivity. We have investigated the phonon dispersion relation in the phonon glass-electron crystal material Ba8Ga16Ge30 using neutron triple-axis spectroscopy. The results disclose unambiguously the theoretically predicted avoided crossing of the rattler modes and the acoustic-phonon branches. The observed phonon lifetimes are longer than expected, and a new explanation for the low k(L) is provided.

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