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Large Thermopower in Metallic Oxides: Misfit Cobaltites and Mangano-Ruthenates

Sylvie Hebert·Christine Martin·Antoine Maignan·Raymond Fresard·Jiri Hejtmanek·Bernard Raveau
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Abstract

Two different kinds of metal transition oxides have been studied for their large thermopower values. The first one corresponds to the Tl-based misfit cobaltite which is a hole-doped metal. We demonstrate that the partial Bi-substitution for Tl in this phase induces an increase of the room temperature (RT) thermopower (TEP) value. Same result is obtained with the new Pb_{1/3}SrCoO_{3+delta} misfit corresponding to the Tl complete replacement by lead. Simultaneously, the T dependence of their resistivity exhibits a re-entrance below 70-90K where a large negative magnetoresistance is observed. Magnetic measurements reveal a strong interplay between spins and charges for this class of materials. Electron-doped (n-type) perovskite manganites are a second class of potential candidates for applications. In particular, the Ru^{4+/5+} substitution for Mn in the CaMnO_3 semi-conductor induces a drastic drop of the resistivity values. Metals with large RT TEP values and not too large thermal conductivities are generated. A comparison with best known materials, Bi_2Te_3 and NaCo_2O_4 is made.

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Sylvie Hebert, Christine Martin, Antoine Maignan, Raymond Fresard, Jiri Hejtmanek, Bernard Raveau. 2001-10-12. Large Thermopower in Metallic Oxides: Misfit Cobaltites and Mangano-Ruthenates. https://arxiv.org/abs/cond-mat/0110270

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