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

Ca 3− x Ce x Co 4− y Ni y O 9+ δ materials were prepared by the sol–gel method, and the effects of Ni, Ce co-doping on the thermoelectric properties of Ca 3 Co 4 O 9+ δ were systematically investigated from 20 K to 350 K. The thermal conductivities of co-doped specimens decreased significantly compared with that of pure Ca 3 Co 4 O 9+ δ , and the opposite trend in thermopower was observed. Ni, Ce co-doping considerably enhanced the thermoelectric responses of Ca 3 Co 4 O 9+ δ compared with those of pure and Ce single-doped Ca 3 Co 4 O 9+ δ . A maximum thermoelectric figure of merit of 0.022 was obtained from Ca 2.9 Ce 0.1 Co 3.9 Ni 0.1 O 9+ δ at 350 K. This value is approximately 9-fold higher than that obtained from Ca 3 Co 4 O 9+ δ and 1.4-fold higher than that from Ca 2.9 Ce 0.1 Co 4 O 9+ δ , which indicates good thermoelectric performance. Overall, results demonstrate that Ni, Ce co-doping effectively improves the thermoelectric properties of Ca 3 Co 4 O 9+ δ systems. [ABSTRACT FROM AUTHOR]