Effects of Ni, Pd and Pt substitutions on thermoelectric properties of cosi alloys

Hui Sun, Xu Lu, Donald T. Morelli

    Research output: Research - peer-reviewArticle

    • 8 Citations

    Abstract

    Ni-, Pd- and Pt-substituted CoSi samples have been prepared by an arc melting and annealing procedure. The x-ray diffraction and scanning electron microscopy results show that Ni and Pd are effective n-type dopants for CoSi, while Pt is immiscible with CoSi and forms an impurity phase with a possible chemical formula of PtCoSi2. The thermoelectric properties were measured from 80 K to 300 K. For Ni- and Pd-doped samples, the electrical resistivity and Seebeck coefficient decrease simultaneously due to the increasing carrier concentration. For Pt-substituted samples, the electrical resistivity also decreases. However, this reduction is thought to be not due to an increase in carriers but rather to originate from the effect of the Pt-rich impurity phase at the grain boundaries. The Seebeck coefficient is not affected by 1% Pt substitution; however, further increase of the Pt level also causes a decrease in the Seebeck coefficient. The room-temperature power factor is 63 μW K-2 cm-1 for pure CoSi and 73 μW K-2 cm-1 for the Co0.99Pt0.01Si sample. Although the thermal conductivity is reduced for both n-type-doped and Pt-substituted samples around 80 K, the room-temperature values are still close to that of pure CoSi. As a result, ZT of 0.13 is obtained at room temperature for Co 0.99Pt0.01Si, an 18% increase compared with CoSi.

    LanguageEnglish (US)
    Pages1352-1357
    Number of pages6
    JournalJournal of Electronic Materials
    Volume42
    Issue number7
    DOIs
    StatePublished - Jul 2013

    Profile

    Seebeck coefficient
    Substitution reactions
    Temperature
    substitutes
    Impurities
    Seebeck effect
    room temperature
    impurities
    electrical resistivity
    Carrier concentration
    Thermal conductivity
    Grain boundaries
    Melting
    Diffraction
    Doping (additives)
    Annealing
    X rays
    Scanning electron microscopy
    arc melting
    x ray diffraction

    Keywords

    • CoSi
    • impurity phase
    • Ni doping
    • Pd doping
    • Pt substitution
    • thermoelectric properties

    ASJC Scopus subject areas

    • Electrical and Electronic Engineering
    • Electronic, Optical and Magnetic Materials
    • Condensed Matter Physics
    • Materials Chemistry

    Cite this

    Effects of Ni, Pd and Pt substitutions on thermoelectric properties of cosi alloys. / Sun, Hui; Lu, Xu; Morelli, Donald T.

    In: Journal of Electronic Materials, Vol. 42, No. 7, 07.2013, p. 1352-1357.

    Research output: Research - peer-reviewArticle

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    AB - Ni-, Pd- and Pt-substituted CoSi samples have been prepared by an arc melting and annealing procedure. The x-ray diffraction and scanning electron microscopy results show that Ni and Pd are effective n-type dopants for CoSi, while Pt is immiscible with CoSi and forms an impurity phase with a possible chemical formula of PtCoSi2. The thermoelectric properties were measured from 80 K to 300 K. For Ni- and Pd-doped samples, the electrical resistivity and Seebeck coefficient decrease simultaneously due to the increasing carrier concentration. For Pt-substituted samples, the electrical resistivity also decreases. However, this reduction is thought to be not due to an increase in carriers but rather to originate from the effect of the Pt-rich impurity phase at the grain boundaries. The Seebeck coefficient is not affected by 1% Pt substitution; however, further increase of the Pt level also causes a decrease in the Seebeck coefficient. The room-temperature power factor is 63 μW K-2 cm-1 for pure CoSi and 73 μW K-2 cm-1 for the Co0.99Pt0.01Si sample. Although the thermal conductivity is reduced for both n-type-doped and Pt-substituted samples around 80 K, the room-temperature values are still close to that of pure CoSi. As a result, ZT of 0.13 is obtained at room temperature for Co 0.99Pt0.01Si, an 18% increase compared with CoSi.

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