Stabilization of the cubic perovskite in the system La1-xBaxCo1-yFeyO3-d and its electrochemical preformance as cathode materiales for intermediate temperature solid oxyde fuel cell
C. MARTINEZ SETEVICH; F. PRADO; D.Z. DE FLORIO; A. CANEIRO
JOURNAL OF POWER SOURCES
ELSEVIER SCIENCE BV
Lugar: Amsterdam; Año: 2014 vol. 247 p. 264 - 264
The effects of the substitution of Co by Fe on the crystal chemistry and electrode reaction of the system La1exBaxCo1eyFeyO3ed (0.7 x 0.9), are investigated. The incorporation of Fe stabilizes the cubic perovskite and suppresses the structural transformation of La1exBaxCoO3ed from a metastable cubic perovskite to a hexagonal phase below 900 C. The linear expansion decreases with the replacement of Co by Fe. The lowest expansion coefficient value, a w 20.5 106 K1, was obtained for the samples with Fe content y ¼ 0.6. AC impedance spectroscopy measurements on symmetrical cells reveal the presence of an intermediate (IF) and a low (LF) frequency contributions at T 600 C. The LF arc varies with the pO2, at 700 C, according to a power law with exponent n ¼ 1, indicating oxygen diffusion through the porous of the electrode. The minimum Rp value (0.6 U cm2 at 600C) was obtained for La0.3Ba0.7Co0.6Fe0.4O3d. At constant temperature, T ¼ 750 C, only the IF contribution varies at a rate of 3 104 U cm2 h1, while the LF contribution remains constant. Experimental data suggest the growth of the IF arc is caused by the mismatch in the expansion coefficients of the electrode and electrolyte.