The effect of ZrO2 dispersion on the thermoelectric power factor of Ca3Co4O9

In the present study, Ca3Co4O9/ZrO2 composites of various compositions have been synthesized by dispersing the ZrO2 particles in the Ca3Co4O9 matrix and their thermoelectric properties are investigated as a function of temperature from room temperature to 553 K. For the prepared composite samples, phase purity and microstructure are analyzed. X-ray diffraction studies show that no unwanted reaction has occurred between Ca3Co4O9 and ZrO2 particles during the final sintering process. From scanning electron micrographs, it is observed that all samples show randomly oriented plate-like grains. Furthermore, the electrical resistivity measurement showed that all composite samples exhibit lower electrical resistivity than the pure Ca3Co4O9. The maximum Seebeck coefficient of 177.35 μV/K at 553 K is achieved for the ZrO2 dispersed Ca3Co4O9 sample. A significant improvement of the power factor (S2σ) has been realized in the prepared composite sample containing 8 wt% ZrO2 which is approximately 40% higher than the pure Ca3Co4O9 at 553 K. The improved power factor achieved for Ca3Co4O9-8 wt% ZrO2 composite sample is mainly due to the obvious decrease in electrical resistivity.