Stabilization of the cubic perovskite in the system La1-xBaxCo1-yFeyO3-d (0.7 < x < 0.9) and its electrochemical performance as cathode materials for IT-SOFC

C.SETEVICH; F. PRADO; D. Z. 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 La1-xBaxCo1-yFeyO3-δ (LBCF) for high Ba contents (0.7 ≤ x ≤ 0.9), is investigated. The incorporation of Fe stabilizes the cubic perovskite phase and suppresses the structural transformation of the La1-xBaxCoO3-δ materials from a metastable cubic perovskite to a hexagonal phase at temperatures below 900 °C. Impedance spectroscopy measurements of the electrode polarization resistance reveal three different contributions at high (HF), intermediate (IF) and low frequency (LF). While the IF polarization resistance is affected by the chemical composition of the electrode, the LF contribution varies with the oxygen partial pressure, at 700 °C, according to a power law with exponent n = -1, indicating oxygen diffusion through the porous of the electrode. The minimum polarization resistance (Rp = 0.6 Ω cm2 at 600 °C) is obtained for La0.3Ba0.7Co0.6Fe0.4O3-δ, that is, the sample with the lowest Fe and Ba contents. These Rp values are larger than those reported for similar electrodes prepared with La1-xBaxCoO3- 600°C). However, the structural stability of these cubic perovskites at intermediate temperatures is what makes them of interest as mixed conductor.