Abstract
We have prepared polycrystalline specimens of [Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> CoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3.1</sub> ] <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.62</sub> CoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> (0 les x les 0.03) using the conventional solid-state reaction method, and investigated the Pb substitution effect on the TE properties. With the Pb substitution, both the electrical resistivity and Seebeck coefficient do not change drastically. This is attributed to the carrier concentration. Seebeck and Hall coefficient measurements reveal that the major charge carriers in the samples are holes, however, the carrier concentration does not change drastically with increasing x. The magnetic susceptibility measurements also show that Pb ions take divalent state in the rock salt type [Ca <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> CoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ] block layer. The valence state of Co ions in the CdI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> type [CoO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> ] sheet was 3.1+ and that of Co ions in the block layer was 3.6+. The dimensionless figure of merit for the x = 0 sample at room temperature was 0.02, which is approximately equal to the corresponding values of a polycrystalline sample of NaCo <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sub>
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