High-Temperature Thermoelectric Properties of Double Perovskite Oxides

Transition metal oxide-based thermoelectric materials are interesting owing to their high thermal stability, low toxicity, low cost and the ease with which their electronic properties can be engineered by changing morphology, doping and stoichiometry. Although several interesting thermoelectric oxides have been reported thus far, but reducing the lattice thermal conductivity while maintaining the good electrical conductivity to get optimum thermoelectric performance is still a challenge. In addition, many oxide systems are not well investigated as yet for their potential to convert waste heat into electricity using the Seebeck effect. In this work, we have explored the structural and thermoelectric properties of Bi doped Sr2CoRuO6 double perovskites. Phase purity and structural characteristics of samples are explored using the Rietveld refinement of powder X-ray diffraction data. The electrical resistivity decreases with doping due to the much larger and well-connected grains in Bi containing samples. The Seebeck coefficient changes its sign from negative to positive with increasing doping content indicating hole doping. The thermal conductivity of the samples decreases with increasing doping due to the soft chemical bonding and heavy atomic mass of Bi atoms. The improvement in transport properties of Bi doped samples led to a large power factor of 1.87 × 10-4 W/m· K2 and a thermoelectric figure-of-merit of 0.24 for the x = 0.8 sample at 668 K. These results show that doping is an effective approach for enhancing the thermoelectric properties of perovskite oxides