High temperature transport properties of Ca3−xNaxCo4O9 system

Ca3−xNaxCo4O9 polycrystalline samples have been prepared using a hot-pressing technique and their thermoelectric properties were carefully studied in air from room temperature to 1000 K. With the substitution of Na+ for Ca2+, the resistivity (ρ) monotonically decreased, while the thermoelectric power (S) slightly increased simultaneously. Element substitution was demonstrated to be an effective means to adjust the thermal conductivity (κ). These results suggest that there exist a potential for improving the thermoelectric performance of Ca3Co4O9 system.