A NEW CANDIDATE FOR THE SOLID OXIDE FUEL-CELL CATHODE, Y0.9CA0.1FEO3 - ELECTRICAL-TRANSPORT PROPERTIES AND DEFECT STRUCTURE

The total electrical conductivity, ionic conductivity, and thermopower have been measured as functions of temperature (900 less than or equa l to T (degrees C) less than or equal to 1100) and oxygen partial pres sure (10(-16) less than or equal to P-o2/atm less than or equal to 1) on the system of Y1-xCaxFeO3 (x = 0.1), a newly proposed solid oxide f uel cell (SOFC) cathode material. The majority ionic carriers are iden tified as oxygen ions via electrotransport experiments. The ionic cond uctivity, which is in the range of 10(-4) to 10(-2) S/cm with an activ ation energy of 1.6 eV in air, tends to increase with increasing P-o2 in oxidizing atmospheres and with decreasing P-o2 in reducing atmosphe res. The defect structure of Y1-xCaxFeO3 system is thus explained on t he basis of anti-Frenkel disorder. Thermodynamic stability of the syst em is also discussed.