Comparative study of the electrochemical response of cobaltites with high Ba content as IT-SOFC cathode material and its relation with the crystal structure

C.SETEVICH; F. PRADO; D. Z. FLORIO; A. CANEIRO

Campos do Jordao

Encuentro; XII Encontro da SBPMAT; 2013

Sociedade Brasilera de Materiales

The polarization resistance (Rp) of the cobaltites with high Ba content: Ba0.5Sr0.5Co0.8Fe0.2O3-BSCFBaCo0.7Fe0.2Nb0.1O3-BCFNLa0.5Ba0.5CoO3-(LBC5) La0.3Ba0.7CoO3-(LBC7)and BaCoO3-(BCO) and the effects on Rp of the structural transformation from a cubic perovskite to a hexagonal phase [1,2] reported in some of these compounds have been investigated by impedance spectroscopy using symmetrical cells in the temperature range, 400 ≤ T ≤ 750 °C , in air. Four different electrode configurations using porous layers of the cobaltites, a composite of cobaltite+Ce0.9Gd0.1O1.95 (GDC) and GDC were prepared according to the following configurations: A) cobaltite / dense GDC B) cobaltite / porous GDC / dense GDC C) cobaltite / Cobaltite+GDC Composite / porous GDC / dense GDC D) Cobaltite / Cobaltite + porous GDC (combustion method) / dense GDC. For all the compositions, the minimum Rp value was obtained with configuration D. The incorporation of the porous GDC layer, the intermediate layer of the composite Cobaltite+GDC with the GDC material prepared using the gel-combustion method improves the performance of the electrode. For example, the Rp values at 600 °C, in air, were 0.05  cm2 for LBC and BSCF. These results indicate that the electrode configuration is very important for developing IT-SOFC cathode with low Rp value. On the other hand, our experimental data suggest that the effects on the polarization resistance of the structural transformation at intermediate temperatures from a metastable perovskite phase to a hexagonal phase reported for BSCF, BCFN and LBC7 are negligible. . [1] C. Setevich, L. Mogni, A. Caneiro, F. Prado. J. Electrochem. Soc. 159 (2012) B73-B80. [2] S. ?varcová, K. Wiik, J. Tolchard, H. Bouwmeester, Tor Grande, Solid State Ionics, 178 (2008) 1787-1791.