Thermoelectric properties of delafossite-related layered metal oxides

Michitaka Ohtaki, Yusuke Kubo, Koichi Eguchi

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    12 Citations (Scopus)

    Abstract

    Thermoelectric properties of layered metal oxides NaxCoO2 in a delafossite (CuFeO2)-related crystal structure are investigated, and a possible mechanism of p-type metallic conduction leading to outstanding thermoelectric performance as an oxide is discussed in terms of crystal chemistry. Sintered samples of NaxCoO2 (x≈0.5) were prepared from Na2CO3 and Co3O4 through the conventional solid state reaction by firing in air. Probably due to losses of Na during firing, electrical properties of the oxides are revealed to be sensitive to the heating atmosphere. The oxides show almost temperature-independent electrical conductivities of >102 S cm-1 up to 1000 K, being accompanied by the positive Seebeck coefficients of 100 - 200 μV K-1 which increase linearly with temperature. Although a poor sinterability of our samples at the present state limits the conductivity to the values lower than those previously reported, the oxide shows a power factor value of >6×10-4 W m-1K-2 at 1000 K. Since the thermal conductivity of the oxides was measured as 1.5 - 2.5 W m-1K-1 at room temperature, and is usually expected to become lower at higher temperatures, the maximum figure of merit is anticipated to reach >0.4×10-3 K-1. The oxide is thereby confirmed to be the most promising p-type oxide candidate so far investigated.

    Original languageEnglish
    Title of host publicationInternational Conference on Thermoelectrics, ICT, Proceedings
    Editors Anon
    PublisherIEEE
    Pages559-562
    Number of pages4
    Publication statusPublished - 1998
    EventProceedings of the 1998 17th International Conference on Thermoelectrics, ICT - Nagoya, Jpn
    Duration: May 24 1998May 28 1998

    Other

    OtherProceedings of the 1998 17th International Conference on Thermoelectrics, ICT
    CityNagoya, Jpn
    Period5/24/985/28/98

    Fingerprint

    Oxides
    Metals
    Crystal chemistry
    Temperature
    Seebeck coefficient
    Solid state reactions
    Thermal conductivity
    Electric properties
    Crystal structure
    Heating
    Air

    All Science Journal Classification (ASJC) codes

    • Engineering(all)

    Cite this

    Ohtaki, M., Kubo, Y., & Eguchi, K. (1998). Thermoelectric properties of delafossite-related layered metal oxides. In Anon (Ed.), International Conference on Thermoelectrics, ICT, Proceedings (pp. 559-562). IEEE.

    Thermoelectric properties of delafossite-related layered metal oxides. / Ohtaki, Michitaka; Kubo, Yusuke; Eguchi, Koichi.

    International Conference on Thermoelectrics, ICT, Proceedings. ed. / Anon. IEEE, 1998. p. 559-562.

    Research output: Chapter in Book/Report/Conference proceedingConference contribution

    Ohtaki, M, Kubo, Y & Eguchi, K 1998, Thermoelectric properties of delafossite-related layered metal oxides. in Anon (ed.), International Conference on Thermoelectrics, ICT, Proceedings. IEEE, pp. 559-562, Proceedings of the 1998 17th International Conference on Thermoelectrics, ICT, Nagoya, Jpn, 5/24/98.
    Ohtaki M, Kubo Y, Eguchi K. Thermoelectric properties of delafossite-related layered metal oxides. In Anon, editor, International Conference on Thermoelectrics, ICT, Proceedings. IEEE. 1998. p. 559-562
    Ohtaki, Michitaka ; Kubo, Yusuke ; Eguchi, Koichi. / Thermoelectric properties of delafossite-related layered metal oxides. International Conference on Thermoelectrics, ICT, Proceedings. editor / Anon. IEEE, 1998. pp. 559-562
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    abstract = "Thermoelectric properties of layered metal oxides NaxCoO2 in a delafossite (CuFeO2)-related crystal structure are investigated, and a possible mechanism of p-type metallic conduction leading to outstanding thermoelectric performance as an oxide is discussed in terms of crystal chemistry. Sintered samples of NaxCoO2 (x≈0.5) were prepared from Na2CO3 and Co3O4 through the conventional solid state reaction by firing in air. Probably due to losses of Na during firing, electrical properties of the oxides are revealed to be sensitive to the heating atmosphere. The oxides show almost temperature-independent electrical conductivities of >102 S cm-1 up to 1000 K, being accompanied by the positive Seebeck coefficients of 100 - 200 μV K-1 which increase linearly with temperature. Although a poor sinterability of our samples at the present state limits the conductivity to the values lower than those previously reported, the oxide shows a power factor value of >6×10-4 W m-1K-2 at 1000 K. Since the thermal conductivity of the oxides was measured as 1.5 - 2.5 W m-1K-1 at room temperature, and is usually expected to become lower at higher temperatures, the maximum figure of merit is anticipated to reach >0.4×10-3 K-1. The oxide is thereby confirmed to be the most promising p-type oxide candidate so far investigated.",
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    AB - Thermoelectric properties of layered metal oxides NaxCoO2 in a delafossite (CuFeO2)-related crystal structure are investigated, and a possible mechanism of p-type metallic conduction leading to outstanding thermoelectric performance as an oxide is discussed in terms of crystal chemistry. Sintered samples of NaxCoO2 (x≈0.5) were prepared from Na2CO3 and Co3O4 through the conventional solid state reaction by firing in air. Probably due to losses of Na during firing, electrical properties of the oxides are revealed to be sensitive to the heating atmosphere. The oxides show almost temperature-independent electrical conductivities of >102 S cm-1 up to 1000 K, being accompanied by the positive Seebeck coefficients of 100 - 200 μV K-1 which increase linearly with temperature. Although a poor sinterability of our samples at the present state limits the conductivity to the values lower than those previously reported, the oxide shows a power factor value of >6×10-4 W m-1K-2 at 1000 K. Since the thermal conductivity of the oxides was measured as 1.5 - 2.5 W m-1K-1 at room temperature, and is usually expected to become lower at higher temperatures, the maximum figure of merit is anticipated to reach >0.4×10-3 K-1. The oxide is thereby confirmed to be the most promising p-type oxide candidate so far investigated.

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