Thermoelectric properties of polycrystalline La1−xSrxCoO3

Thermoelectric properties of polycrystalline La1−xSrxCoO3, where Sr2+ is substituted in La3+ site in perovskite-type LaCoO3, have been investigated. Sr-doping increases the electrical conductivity (σ) of La1−xSrxCoO3, and also decreases the Seebeck coefficient (S) for 0.01⩽x⩽0.40. A Hall coefficient measurement reveals that the increase in electrical conductivity arises from increases in both carrier concentration and the Hall mobility. The decrease in the Seebeck coefficient is caused by a decrease in carrier effective mass as well as increase in carrier concentration. The highest power factor (σS2) is 3.7×10−4 W m−1 K−2 at 250 K for x=0.10. The thermal conductivity (κ) is about 2 W m−1 K−1 at 300 K for 0⩽x⩽0.04, and increases for x⩾0.05 because of an increase in heat transport by conductive carrier. The thermoelectric properties of La1−xSrxCoO3 are improved by Sr-doping, and the figure of merit (Z=σS2 κ−1) reaches 1.6×10−4 K−1 for x=0.06 at 300 K (ZT=0.048). For heavily Sr-doped samples, the thermoelectric properties diminish mainly because of the decrease in the Seebeck coefficient and the increase in thermal conductivity.