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 studi ed as a function of temperature and oxygen activity. The thermochemica l properties of these compositions under a reducing atmosphere appear to follow the boundaries set between the two end members, LaFeO3 and L aCoO3, but the electrical properties are closer to those of LaFeO3. Th e Sr content (x less than or equal to 0.4) does not seem to have a sig nificant effect on the high-temperature phase stability. Dissociation of these compositions under a reducing atmosphere occurred gradually b y the formation of transient compounds. The major transient compounds formed during dissociation could be represented by a general formula o f (La,Sr) (Fe,Co)O-4. Upon further reduction, these oxides dissociated to La2O3, SrO, Co, and Fe. (C) 1995 Academic Press, Inc.