Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-delta) (BSCF) and La_(0.6)Ba_(0.4)Co_(0.2)Fe_(0.8)O_(3-delta) (LBCF) cathodes prepared by combined citrate-EDTA method for IT-SOFCs

摘要

The potential candidates for IT-SOFCs cathode materials, Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-delta) (BSCF) and La_(0.6)Ba_(0.4)Co_(0.2)Fe_(0.8)O_(3-delta) (LBCF), were synthesized by the combined citrate-EDTA method. The BSCF and LSCF aqueous precursors solutions were prepared from Sr(NO_3)_2, Ba(NO_3)_2, La(NO_3)_3 centre dot 6H_2O, Co(NO_3)_2 centre dot 6H_2O, Fe(NO_3)_3 centre dot 9H_2O, citric acid and EDTA-NH_3. BSCF precursor solutions with different pH values were dried at 130 deg 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 deg 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 deg C, respectively. On the other hand, the cathode polarization resistances of the LBCF electrode were slightly higher than those of the BSCF electrode.