Preparation, crystal structure and high-temperature thermoelectric properties of double perovskite-type rare-earth cobalt ruthenium oxides

Rare-earth cobalt ruthenium oxides Ln(2)CoRuO(6) (Ln=La, Pr, Nd, Sm, Eu and Gd) having the double perovskite-type structure were prepared at 1673 K in air. Rietveld analysis of the X-ray diffraction patterns revealed that the oxides crystallized in monoclinic cells with space group P2(1)/n (No. 14). Co/Ru disorder up to 10% was observed at each of the octahedral site in GdCoRuO6. Ln(2)CoRuO(6) oxides were p-type semiconductors with Seebeck coefficient of 180-290 mu V center dot K-1 at 400 K and 72-79 mu V center dot K-1 at 1073 K. The power factors at 1073 K were 1.9-4.3 x 10(-6) W center dot K-2 center dot m(-1).