各種基板上にパルスレーザー蒸着法を用いて作製した[Ca_2CoO3_]_xCoO_2薄膜の熱電特性と微細組織

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We have fabricated c-axis oriented thin films of the oxide thermoelectric material Ca_3Co_4O_9 (CCO) on MgO (100), SrTiO_3 (100) (STO), YSZ polycrystal and YSZ (100) substrates by pulsed laser deposition. The resistivity of CCO thin films on SrTiO_3 and YSZ substrates hardly varied with increasing temperature from 300 to 700 K. On the other hand, the resistivity of the films on MgO was relatively high, because of an impurity phase grown on the surface and the change of lattice constant at high temperature. From the microstructure of the CCO films on STO observed by transmission electron microscopy (TEM) techniques, a main structure of cobaltite [Ca_2CoO_3]xCoO_2 has been found with identical a, b_1 and c parameters: a=0.48 nm, b=0.45 nm and c=1.07 nm. The composition ratios of the main phase and secondary phase in the CCO films were Ca:Co=0.98:1.0 and Ca:Co=0.39:1.0, respectively.
社団法人日本セラミックス協会の論文
2002-12-01