THERMOCHEMICAL STABILITY, ELECTRICAL-CONDUCTIVITY, AND SEEBECK COEFFICIENT OF SR-DOPED LACO0.2FE0.8O3-DELTA

Phase stability, oxygen content, electrical conductivity, and Seebeck coefficient of La1-xSrxCo0.2Fe0.8O3-delta (x = 0, 0.2, 0.4) were studied as a function of temperature and oxygen activity. The thermochemical properties of these compositions under a reducing atmosphere appear to follow the boundaries set between the two end members, LaFeO3 and LaCoO3, but the electrical properties are closer to those of LaFeO3. The Sr content (x less than or equal to 0.4) does not seem to have a significant effect on the high-temperature phase stability. Dissociation of these compositions under a reducing atmosphere occurred gradually by the formation of transient compounds. The major transient compounds formed during dissociation could be represented by a general formula of (La,Sr) (Fe,Co)O-4. Upon further reduction, these oxides dissociated to La2O3, SrO, Co, and Fe. (C) 1995 Academic Press, Inc.