Electrical conductivity and thermoelectric power studies of solution-combustion-processed Ca2.76Cu0.24Co4O9

Nanocrystalline Ca2.76Cu0.24Co4O9 powders (25 nm in crystallite size) are synthesized by the solution combustion method, using aspartic acid as the combustion fuel. In this study, we discuss the effect of sintering temperature on the microstructure and thermoelectric properties of Ca2.76Cu0.24Co4O9. The density and grain size increase with an increase in sintering temperature. The Ca2.76Cu0.24Co4O9 sintered at 900 °C shows the largest value of electrical conductivity and Seebeck coefficient, resulting in the largest power factor (3.8×10−4 W m−1 K−2 at 800 °C). This value is more than 22 times larger than that of the Ca2.76Cu0.24Co4O9 sintered at 940 °C (1.7×10−5 W m−1 K−2 at 800 °C).