Effect of Y doping at Co site on thermoelectric properties of Ca3Co4O9

In this work, our effort was to improve the thermoelectric properties of Ca3Co4O9 thermoelectric material. Ca3Co4-xYxO9 polycrystalline thermoelectric ceramics have been fabricated by sol-gel method plus spontaneous combustion and cold isostatic pressing process. The structure, surface topography and thermoelectric properties of Ca3Co4-xYxO9 polycrystalline thermoelectric were investigated by X-ray diffraction (XRD), SEM and ZEM3, respectively. The results showed that Y doping affected the microstructure and thermoelectric performance remarkable. With the increasing of Y doping, the electrical conductivity had a maximum value, and thermal conductivity has a minimum value. Seebeck coefficient gradually increased with Y doping content increasing always. The figure of merit was 0.07 at 673K for the Ca3Co3.7Y0.3O9 sample. The results showed that the thermoelectric performance of Ca3Co4O9 could be improved 39% with the substitution of Y than the un-doped