Ba0.5Sr0.5Co0.8Fe0.2O3-δ (BSCF) and La0.6Ba0.4Co0.2Fe0.8O3-δ (LBCF) cathodes prepared by combined citrate-EDTA method for IT-SOFCs

The potential candidates for IT-SOFCs cathode materials, Ba0.5Sr0.5Co0.8Fe0.2O3-delta (BSCF) and La0.6Ba0.4Co0.2Fe0.8O3-delta (LBCF), were synthesized by the combined citrate-EDTA method. The BSCF and LSCF aqueous precursors solutions were prepared from Sr(NO3)(2), Ba(NO3)(2), La(NO3)(3)center dot 6H(2)O, Co(NO3)(2)center dot 6H(2)O, Fe(NO3)(3)center dot 9H(2)O, citric acid and EDTA-NH3. BSCF precursor solutions with different pH values were dried at 130 degrees C and subsequently calcined at various temperatures. Symmetrical electrochemical cells consisting of porous BSCF or LBCF electrodes and a GDC electrolyte were fabricated by the screen-printing technique, and the cathode performance of the interfaces between the porous electrode (BSCF or LBCF) and GDC electrolyte was investigated at intermediate temperatures (500-700 degrees C) using AC impedance spectroscopy. The pH value of the precursor solution did not affect the phase evolution behavior of the BSCF powder. On the other hand, it appears that a low pH value results in the calcined BSCF powder having a more porous microstructure. The cathode performances of the BSCF and LBCF electrodes were sensitive to the powder preparation conditions. The BSCF electrode prepared from the precursor solution with a pH value of 8 showed low polarization resistance, and its area specific resistances (ASR) were 1.1, 0.15 and 0.035 Omega cm(2) at 500, 600 and 700 degrees C, respectively. On the other hand, the cathode polarization resistances of the LBCF electrode were slightly higher than those of the BSCF electrode. (c) 2006 Elsevier B.V. All rights reserved.