Thermoelectric properties of Ru-based oxides with a layered structure

RuSr/sub 2/GdCu/sub 2/O/sub 8/ (Ru-1212) has a layered structure in which insulating CuO/sub 2/ plane and conductive RuO/sub 3/ plane are piled up alternatively. Thermoelectric properties of Ru-1212 have been evaluated from room temperature to 600/spl deg/C and these results are compared with those of SrRuO/sub 3/ with a three dimensional perovskite structure. SrRuO/sub 3/ shows a metallic /spl sigma/-T behavior, whereas a semiconducting-like transport is observed in the Ru-1212. At temperatures T<400/spl deg/C, the Seebeck coefficient values of Ru-1212 are larger than those of SrRuO/sub 3/ by more than twice. The thermal conductivity of Ru-1212 is lower than that of SrRuO/sub 3/ whole the measured temperature range. In the viewpoint of Seebeck coefficient and thermal conductivity, making an insulating/conducting superlattice structure is effective to enhance the thermoelectric performance.