Interplay of chemical expansion, Yb valence, and low temperature thermoelectricity in the YbCu2Si2-xGex solid solution

Gloria J. Lehr, Donald T. Morelli

    Research output: Contribution to journalArticle

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    Abstract

    YbCu2Si2 is a promising low temperature thermoelectric material because of the large broad peak in the Seebeck coefficient near 100 K combined with a low electrical resistivity. This behavior is thought to arise from fluctuating, or intermediate, valence effects due to partial occupation of Yb 4f energy states near the Fermi level. Previous studies of the magnetic properties under pressure have demonstrated that the average Yb valence is sensitive to the contraction of unit cell volume. By forming a solid solution of YbCu2Si2 with YbCu2Ge2, an isostructural compound with a larger unit cell volume, here we examine the subtle effects of lattice expansion on the transport properties and average Yb valence. We observe a shift in the peak of the Seebeck coefficient towards higher temperatures, as well as an enhanced power factor in the solid solutions. At the same time, a reduction in thermal conductivity due to alloy scattering enhances the thermoelectric figure of merit. Chemical pressure effects may thus be utilized to control and optimize the thermoelectric properties of these alloys in the cryogenic temperature range.

    Original languageEnglish (US)
    Article number135101
    JournalJournal of Applied Physics
    Volume117
    Issue number13
    DOIs
    StatePublished - Apr 7 2015

    Profile

    valence
    solid solutions
    Seebeck effect
    expansion
    cells
    thermoelectricity
    thermoelectric materials
    pressure effects
    cryogenic temperature
    figure of merit
    occupation
    contraction
    thermal conductivity
    transport properties
    magnetic properties
    electrical resistivity
    shift
    scattering
    energy

    ASJC Scopus subject areas

    • Physics and Astronomy(all)

    Cite this

    Interplay of chemical expansion, Yb valence, and low temperature thermoelectricity in the YbCu2Si2-xGex solid solution. / Lehr, Gloria J.; Morelli, Donald T.

    In: Journal of Applied Physics, Vol. 117, No. 13, 135101, 07.04.2015.

    Research output: Contribution to journalArticle

    Lehr, Gloria J.; Morelli, Donald T. / Interplay of chemical expansion, Yb valence, and low temperature thermoelectricity in the YbCu2Si2-xGex solid solution.

    In: Journal of Applied Physics, Vol. 117, No. 13, 135101, 07.04.2015.

    Research output: Contribution to journalArticle

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