Strong influence of CO2 partial pressure on inhomogeneous Na distributions and the thermoelectric performance of polycrystalline NaCo 2C4

Michitaka Ohtaki, Kimihiro Shouji

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

    2 Citations (Scopus)

    Abstract

    Influence of gas-solid equilibrium and partial pressures of gaseous species was investigated on solid state reactions of Na2CO 3 and Co3O4 for synthesis of bulk sintered bodies of layered thermoelectric oxide NaCo2O4. It was revealed that the presence of CO2 in the reaction atmosphere strongly inhibits the formation reaction of NaCo2O4. However, precise control of the CO2 partial pressure in the oxygen atmosphere enabled us to avoid otherwise significant Na loss during sintering at temperature as high as 900°C, thereby allowing high reaction temperature required for incorporation of Na into the crystal lattice. Selective quantification of the Na species in order to distinguish those within the crystallites and at the grain boundaries revealed that the samples synthesized in the presence of dilute CO2 contain more Na in the crystallites with less Na segregation at the boundaries. Improved interconnection between the grains containing larger amounts of Na was suggested as a reason of higher electrical conductivity and larger Seebeck coefficient of the samples thus obtained, compared to the samples containing the same amount of total Na but synthesized in air.

    Original languageEnglish
    Title of host publicationProceedings - ICT'05
    Subtitle of host publication24th International Conference on Thermoelectrics
    Pages472-475
    Number of pages4
    Volume2005
    DOIs
    Publication statusPublished - Dec 1 2005
    EventICT'05: 24th International Conference on Thermoelectrics - Clemson, SC, United States
    Duration: Jun 19 2005Jun 23 2005

    Other

    OtherICT'05: 24th International Conference on Thermoelectrics
    CountryUnited States
    CityClemson, SC
    Period6/19/056/23/05

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    All Science Journal Classification (ASJC) codes

    • Engineering(all)

    Cite this

    Ohtaki, M., & Shouji, K. (2005). Strong influence of CO2 partial pressure on inhomogeneous Na distributions and the thermoelectric performance of polycrystalline NaCo 2C4 In Proceedings - ICT'05: 24th International Conference on Thermoelectrics (Vol. 2005, pp. 472-475). [1519988] https://doi.org/10.1109/ICT.2005.1519988