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−δ (BSCF) and La0.6Ba0.4Co0.2Fe0.8O3−δ (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)3·6H2O, Co(NO3)2·6H2O, Fe(NO3)3·9H2O, citric acid and EDTA-NH3. BSCF precursor solutions with different pH values were dried at 130 °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 °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 Ω cm2 at 500, 600 and 700 °C, respectively. On the other hand, the cathode polarization resistances of the LBCF electrode were slightly higher than those of the BSCF electrode.