Effects of Sm Doping on the High Temperature Thermoelectric Properties of Ca_3Co_4O(9+δ)-based Compounds

Ca3-xSmxCo4O9+δ(x=0, 0.15, 0.3 and 0.45) polycrystalline samples were prepared by using sol-gel process followed by SPS sintering. Their thermoelectric properties were carefully studied from room temperature to 1000K. The substitution of Sm for Ca results in the increase of both Seabeck coefficient and electrical resistivity, which could be attributed to the decrease of carrier concentrations. The Sm substituted samples (x=0.15, 0.3) have lower thermal conductivity than Ca3Co4O9+δ due to their lower electronic and lattice thermal conductivities. The dimensionless figure of merit ZT reaches 0.3 at 1000K for the sample of Ca2.7Sm0.3Co4O9+δ