High-temperature Thermoelectric and Microstructural Characteristics of Ga Substituted on the Co-site in Cobalt-based Oxides

Ngo Van Nong, S. Yanagiya, Monica Sonne, Nini Pryds, M. Ohtaki

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    Abstract

    The effects of Ga substitution on the Co-site on the high-temperature thermoelectric properties and microstructure are investigated for the misfitlayered Ca3Co4O9 and the complex perovskite-related Sr3RECo4O10.5 (RE = rare earth) cobalt-based oxides. For both systems, substitution of Ga for Co results in a simultaneous increase in the Seebeck coefficient (S) and the electrical conductivity (σ), and the influence is more significant in the high temperature region. The power factor (S 2 σ) is thereby remarkably improved by Ga substitution, particularly at high temperatures. Texture factor calculations using x-ray diffraction pattern data for pressed and powder samples reveal that the Ga-doped samples are highly textured. Microstructure observed by scanning electron microscopy shows very well-crystallized grains for the samples with Ga substitution for Co. Among the Ga-doped samples, Ca3Co3.95Ga0.05O9 shows the best ZT value of 0.45 at 1200 K, which is about 87.5% higher than the nondoped one, a considerable improvement.
    Original languageEnglish
    JournalJournal of Electronic Materials
    Volume40
    Issue number5
    Pages (from-to)716-722
    ISSN0361-5235
    DOIs
    Publication statusPublished - 2011

    Keywords

    • Magnetic refrigeration

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