Electrode reaction of Sr_1–xLa_xCo_0.8Fe_0.2O_3–δ with x = 0.1 and 0.6 on Ce_0.9Gd_0.1O_1.95 at 600 ? T ? 800 °C

Nicolas Grunbaum (1, 2) , Laurent Dessemond (2) , Jacques Fouletier (2) , Fernando Prado (1) , Alberto Caneiro (1)

1 Instituto Balseiro [Bariloche]
2 LEPMI - Laboratoire d'Electrochimie et de Physico-chimie des Matériaux et des Interfaces

The electrode reaction of the perovskite phases Sr_1−xLa_xCo_0.8Fe_0.2O_3−δ (x = 0.1 and 0.6) on Ce_0.9Gd_0.1O_1.95 has been investigated by impedance spectroscopy in the temperature range 600 ≤ T ≤ 800 °C. Thick porous electrodes (t ~ 20 μm) were sprayed on Ce_0.9Gd_0.1O_1.95 and ac impedance spectra were recorded on symmetrical cells at the equilibrium. The analysis of the complex impedance diagrams clearly indicates the presence of two contributions. The low frequency one was assigned to the gas phase oxygen diffusion through the porous electrode and a finite length diffusion (Warburg) impedance was used to describe the high frequency (HF) data. The polarization resistance of the HF impedance contribution (R_w) is higher for x = 0.1 while the activation energy of R_w is higher for x = 0.6. The variations of R_w versus the La content, temperature and thickness indicate that the Warburg-type impedance contains information of both bulk oxygen diffusion and surface processes.

Mots clés: Mixed conductors; Electrode reaction; Cobaltites; SOFC; Impedance spectroscopy

Domaines: Matériaux

Nicolas Grunbaum, Laurent Dessemond, Jacques Fouletier, Fernando Prado, Alberto Caneiro. Electrode reaction of Sr_1–xLa_xCo_0.8Fe_0.2O_3–δ with x = 0.1 and 0.6 on Ce_0.9Gd_0.1O_1.95 at 600 ? T ? 800 °C. Solid State Ionics, 2006, 177 (9-10), pp. 907-913. ⟨10.1016/j.ssi.2006.02.009⟩. ⟨hal-00333651⟩