Thermoelectric properties of polycrystalline La 1−xSr xCoO 3

Abstract

Thermoelectric properties of polycrystalline La 1− x Sr x CoO 3, where Sr 2+ is substituted in La 3+ site in perovskite-type LaCoO 3, have been investigated. Sr-doping increases the electrical conductivity ( σ) of La 1− x Sr x CoO 3, 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 ( σS 2) 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 La 1− x Sr x CoO 3 are improved by Sr-doping, and the figure of merit ( Z= σS 2 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.