OXIDATION REDUCTION BEHAVIOR OF UNDOPED AND SR-DOPED LAMNO3 - DEFECT STRUCTURE, ELECTRICAL-CONDUCTIVITY, AND THERMOELECTRIC-POWER

Seebeck coefficient and electrical conductivity measurements were performed for undoped and Sr-doped LaMnO3 as a function of temperature and oxygen partial pressure. The results of electrical conductivity showed typical p-type behavior. As reduction proceeded, the electrical conductivity of these LaMnO3-based perovskites decreased with P 1 4O. The analysis of the electrical conductivity data was performed by extending the defect model from a previous thermogravimetric (TG) study. The measured Seebeck coefficients were found to be positive except for the most reducing conditions when the decomposition into multiple phases occurred. The Heikes formula was adopted to interpret the Seebeck coefficient results and to calculate the mobility. These results indicated that the conduction was due to p-type carriers of a localized nature. It was also suggested that the conductivity for these perovskites was dominated by the mobility rather than by the carrier concentration. © 1990.