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 - 272

0378-7753

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  10
6 K
1, 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 La0.3Ba0.7Co0.6Fe0.4O3
d. At constant temperature, T ¼ 750 C, only the IF contribution varies at a rate of 3  10
4 U cm2 h
1, 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.