Lanthanum alkaline-earth manganites as a cathode material in high-temperature solid oxide fuel cells

The effect of RE (RE = Ce and Pr) doping LaMnO3 perovskite on crystallograp hic properties, phase relationships, conductivity, thermal expansion, sinte ring, and reaction with Y2O3-stabilized ZrO2 electrolyte is presented. La1- xRExMnO3 showed a single perovskite phase in the region 0 less than or equa l to x less than or equal to 0.05 for Ce substitution and over the entire c omposition range of Pr content. No effect of RE doping of LaMnO3 on conduct ivity was observed. A decrease in thermal expansion coefficients of LaMnO3 accompanied RE doping. Ce doping of LaMnO3 increased its morphological stab ility and suppressed its reaction with the electrolyte. Ln(1-x)AE(x)MnO(3) (Ln: lanthanum concentration with La, Ce, and Pr, AE = Sr, Ca) materials we re examined as cathodes in solid oxide fuel cells. X-ray diffraction analys is indicated that Ln(1-x)AE(x)MnO(3) (0 less than or equal to x less than o r equal to 0.3) showed a single perovskite phase. Conductivities of these o xides increased with AE content and ranged from 80 to 200 S/cm at 1000 degr ees C in air. and thermal expansion coefficients ranged from 9.5 to 11.6 x 10(-6)/degrees C. Ln(1-x)AE(x)MnO(3) showed less reactivity with the electr olyte compared with La(1-x)AE(x)MnO(3). The cathodic polarization of the (L n(0.8)Sr(0.2))(0.95)MnO3 at 1000 degrees C was 60 mV at 500 nA/cm(2) in air . (C) 1999 The Electrochemical Society. S0013-4651(99)04-013-6. All rights reserved.