| Nano-structured and nano-porous mixed ionic and electronic conducting
Ba0.5Sr0.5Co0.8Fe0.2O3– (BSCF) cathodes with an average grain size ~500 nm and
porosity 30% were processed from sol-gel method using metal organic precursors
and calcined at 950oC for 5 h followed by sintering at 1000oC for 3 h. Crystallization
of the powder was analyzed by X-ray diffraction and found to be dependent on
calcination temperature. The calcined powder was compacted into circular discs
and sintered between 1000o and 1100oC to achieve the desired porosity. Scanning
electron microscopy showed porous BSCF structure, facilitating gas transfer and
maximizing the number of active sites for oxygen reduction reaction at the cathode
of a solid oxide fuel cell. BSCF powder was made into paste and screen printed on
Ce0.8Gd0.2O2– (GDC) electrolyte to form a symmetric cell. Thickness of the BSCF
cathode film is around 4 m. Area specific polarization resistance was measured
in a broad range of temperature (300o-700oC) at the frequency range from 10 MHz
to 0.1 Hz. Impedance measurements show that area-specific resistance for the
symmetric cell with BSCF cathode is 1.74 -cm2 at 600oC. These results are
impressive and demonstrate the potential of BSCF to be used as cathode material
in new-generation SOFCs with GDC as the electrolyte.
[Keywords: SOFC, BSCF cathode, MIEC, Sol-gel, Catalytic activity, Impedance] |
