Mixed Electronic-ionic Conductivity of Perovskite-type Oxides

La0.6Sr0.4Co1-yFeyO3 complex oxide powders were synthesized by a glycine-nitrate process(GNP). The electrical conductivities and the oxygen ionic conductivities of La0.6Sr0.4Co1-y-FeyO3 ceramics were investigated by DC four-terminal method and AC impedance spectroscopy using two-terminal blocking electrodes, respectively. The equivalent circuits for AC impedance spectra were ascertained with respect to measuring temperature. The electrical conductivity of La0.6Sr0.4CoO3 decreased monotonously with the increase of temperature from room temperature to 900℃, while the electrical conductivities of other compositions increased with temperature through the maximum near 600℃ and then decreased. The ionic conductivities of La0.6Sr0.4Co1-yFeyO3 ceramics increased with temperature within the whole measuring temperature range. The electrical conductivities and the ionic conductivities of La0.6Sr0.4Co1-yFeyO3 ceramics enhanced with the increase of Co/Fe ratio under the same measuring temperature. The activation energies for electronic conduction and the activation energies for oxygen ionic conduction of La0.6Sr0.4Co1-yFeyO3 ceramics decreased with the increase of Co/Fe ratio. The ionic transport numbers of La0.6Sr0.4Co1-yFeyO3 increased with the increase of temperature and decreased with the increase of Co/Fe ratio at an identical temperature. La0.6Sr0.4Co1-yFeyO3 ceramics exhibited the ionic conductivities of 4.0×10-2 -6.5℃10-2S·cm-1 and the ionic transport numbers of 4.6×10-5 -1.5×10-4 at 800℃.