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 (sigma) 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 (sigma S-2) is 3.7 x 10(-4)W m(-1) K-2 at 250 K for x = 0.10. The thermal conductivity (kappa) 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 = sigma S-2 K-l) reaches 1.6 x 10(-4) K-1 for x = 0.06 at 300K (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. (C) 2008 Elsevier Inc. All rights reserved.