単結晶を利用したNa_xCoO_2配向セラミックスの熱電特性  [in Japanese] Thermoelectric properties of higtly oriented Na_xCoO_2 ceramics prepared by single cristals  [in Japanese]

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Abstract

NaxCoO<SUB>2</SUB> single crystal has an anisotropy in thermoelectric properties, in which in-plane thermoelectric performance shows an excellent dimensionless value of ZT (Z=S<SUB>2</SUB>⋅m<SUB>-1</SUB>k<SUB>-1</SUB>T). The high thermoelectric performance of a polycrystalline Na<SUB>x</SUB>CoO<SUB>2</SUB>, however, is not yet realizable because of its high electrical resistivity. Therefore, the highly oriented Na<SUB>x</SUB>CoO<SUB>2</SUB> polycrystals were synthesized and their thermoelectric properties were measured. For making the highly oriented Na<SUB>x</SUB>CoO<SUB>2</SUB>, the single crystals were used as starting materials with three kinds of powders; for (a) mixed Na<SUB>2</SUB>CO<SUB>3</SUB> and Co<SUB>3</SUB>O<SUB>4</SUB>, (b) ground Na<SUB>x</SUB>CoO<SUB>2</SUB> polycrystal and (c) Na<SUB>2</SUB>CO<SUB>3</SUB>. Consequently, it was succeeded in the preparation of the highly oriented sample in each case. The electrical resistivity of the oriented Na<SUB>x</SUB>CoO<SUB>2</SUB> ceramics prepared by the (a) powder was about 6.6-8.9 mΩcm. The electrical resistivity of the ceramics, which was prepared by the (b) powder, decreased to 2.5-3.9 mΩcm. The electrical resistivity of the ceramics synthesized by the (c) powder was about 2 mΩcm. The difference of their electrical resistivities was due to the effects of the orientation, the grain boundary resistivity and the content of Na. The maximum power factor was about 500μW/mK<SUP>2</SUP> at 663 K.

Journal

  • Journal of the Japan Society of Powder and Powder Metallurgy

    Journal of the Japan Society of Powder and Powder Metallurgy 49(5), 400-405, 2002-05-15

    Japan Society of Powder and Powder Metallurgy

References:  11

Codes

  • NII Article ID (NAID)
    10008559578
  • NII NACSIS-CAT ID (NCID)
    AN00222724
  • Text Lang
    JPN
  • Article Type
    ART
  • ISSN
    05328799
  • NDL Article ID
    6169400
  • NDL Source Classification
    ZP41(科学技術--金属工学・鉱山工学)
  • NDL Call No.
    Z17-274
  • Data Source
    CJP  NDL  J-STAGE 
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