Oxygen Diffusivity of La0.6Sr0.4Co0.2Fe0.8O3-δ Perovskite Oxide

La0.6Sr0.4Co0.2Fe0.8O3-δ composite oxide was prepared and characterized. Dilatometer and four-probe DC were exploited to investigate the thermal expansion and electrical conductivity, respectively. The thermal expansion curve was linear, but it became steeper at the high temperature region, as a result of the loss of lattice oxygen and the formation of oxygen vacancies. The conductivity increased with temperature up to about 600oC, and then decreased due to the loss of lattice oxygen. The maximum conductivity was more than 300 S cm-1. The chemical diffusion coefficient in La0.6Sr0.4Co0.2Fe0.8O3-δ was estimated by analyzing the conductivity relaxation behavior. The relaxation process of the conductivity change for La0.6Sr0.4Co0.2Fe0.8O3-δ was traced as a function of time, at a fixed temperature. It was found that the chemical diffusion coefficients measured at temperatures 720-770oC vary from 710-8 to 110-7 cm2 S-1. The activation energy for oxygen diffusion in La0.6Sr0.4Co0.2Fe0.8O3-δ, derived from the chemical diffusion coefficient is 40.8±3.6 kJ mol-1.