Abstract
Effects of (Lu, Ni) co-doping on the thermoelectric properties of Ca3Co4O9+delta (CCO) have been systematically investigated from 20 K to 350 K. The electrical resistivity and thermopower of (Lu, Ni) co-doped samples increase, while their thermal conductivity is significantly depressed as compared to that of pristine CCO. The figure of merit (ZT) of co-doped samples is higher than those of Lu-doped samples and pristine CCO. A maximum ZT of 0.0185 is achieved at 350 K for Ca2.9Lu0.1Co3.9Ni0.1O9+delta. We demonstrate that the simultaneous increase of spin entropy and phonon scattering induced by (Lu, Ni) co-doping boosts ZT of CCO. This study indicates that (Lu, Ni) co-doping may promise an effective way to improve thermoelectric properties of the CCO system.