Thermoelectric properties and crystal chemistry of promising oxide candidate NaxCoO2

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    Abstract

    Promising p-type thermoelectric properties of a layered transition metal oxide NaxCoO2 are discussed in terms of crystal chemistry and the conduction mechanism. Highly anisotropic spatial distribution of 3d orbitals coupled with an unusually short Co-Co interatomic distance in the ab plane, along which edge-sharing CoO6 octahedra connecting each other to form the CoO2 sheets, strongly suggest that Co3d dε-dε (t2g-t2g) direct overlapping is plausible for establishing hole conduction in the valence band with a fairly covalent character. An extremely low thermal conductivity (≤1 W/mK) of the oxide is also revealed, implying contribution of the randomly distributed Na vacancies and an inherent advantage of materials with low-dimensional crystal structure. In spite of insufficient densification, sintered bodies fired under atmospheric pressure shows ZT≈0.5. Possible influence of the ionic conduction of Na+ on the thermoelectric properties of the oxide is also examined.

    Original languageEnglish
    Pages (from-to)565-568
    Number of pages4
    JournalUnknown Journal
    Publication statusPublished - 1999

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    Crystal chemistry
    crystal chemistry
    oxide
    Oxides
    transition element
    thermal conductivity
    crystal structure
    atmospheric pressure
    Ionic conduction
    spatial distribution
    Valence bands
    Densification
    Spatial distribution
    Atmospheric pressure
    Vacancies
    Transition metals
    Thermal conductivity
    Crystal structure
    material
    metal oxide

    All Science Journal Classification (ASJC) codes

    • Engineering(all)

    Cite this

    Thermoelectric properties and crystal chemistry of promising oxide candidate NaxCoO2 . / Ohtaki, Michitaka.

    In: Unknown Journal, 1999, p. 565-568.

    Research output: Contribution to journalArticle

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    abstract = "Promising p-type thermoelectric properties of a layered transition metal oxide NaxCoO2 are discussed in terms of crystal chemistry and the conduction mechanism. Highly anisotropic spatial distribution of 3d orbitals coupled with an unusually short Co-Co interatomic distance in the ab plane, along which edge-sharing CoO6 octahedra connecting each other to form the CoO2 sheets, strongly suggest that Co3d dε-dε (t2g-t2g) direct overlapping is plausible for establishing hole conduction in the valence band with a fairly covalent character. An extremely low thermal conductivity (≤1 W/mK) of the oxide is also revealed, implying contribution of the randomly distributed Na vacancies and an inherent advantage of materials with low-dimensional crystal structure. In spite of insufficient densification, sintered bodies fired under atmospheric pressure shows ZT≈0.5. Possible influence of the ionic conduction of Na+ on the thermoelectric properties of the oxide is also examined.",
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