The thermal-transport properties of the Ca3-xAgxCo4O9 system (0 ≤ x ≤ 0.3)

Polycrystalline Ca3-xAgxCo4O9 (0 <= x <= 0.3) samples were prepared by solid-state reaction and their thermo-transport properties were studied from 5 K to room temperature. With the substitution of Ag+ for Ca2+, the internal chemical pressure induced by Ag+ doping has a strong effect on the transport properties of such a strongly correlated Fermi liquid system. The electrical conductivity and the thermoelectric power increase simultaneously because of the enhancement of carrier concentration and the change of carrier mobility. The thermal conductivity decreases monotonically up to x = 0.3 due to the Ag ion acting as a rattler in the system. These results showed that the thermoelectric performance of the Ca3Co4O9 system can be improved by doping with Ag.