Enhanced thermoelectric properties of Ca3Co4O9+δ by Ni, Ce co-doping

Ca3−xCexCo4−yNiyO9+δ materials were prepared by the sol–gel method, and the effects of Ni, Ce co-doping on the thermoelectric properties of Ca3Co4O9+δ were systematically investigated from 20 K to 350 K. The thermal conductivities of co-doped specimens decreased significantly compared with that of pure Ca3Co4O9+δ, and the opposite trend in thermopower was observed. Ni, Ce co-doping considerably enhanced the thermoelectric responses of Ca3Co4O9+δ compared with those of pure and Ce single-doped Ca3Co4O9+δ. A maximum thermoelectric figure of merit of 0.022 was obtained from Ca2.9Ce0.1Co3.9Ni0.1O9+δ at 350 K. This value is approximately 9-fold higher than that obtained from Ca3Co4O9+δ and 1.4-fold higher than that from Ca2.9Ce0.1Co4O9+δ, which indicates good thermoelectric performance. Overall, results demonstrate that Ni, Ce co-doping effectively improves the thermoelectric properties of Ca3Co4O9+δ systems.