Oxides Ba_(1-x) Ca_x Co_0.2 Fe_0.8 O_(3-δ) (x=0,0.5,0.6,0.7) were prepared and their structures, propertied were studied in this thesis. These oxides were employed to fabricate the cathodes for the proton-transport solid oxide fuel cell (P-SOFC) to explore their performance. Modification of the cathodes by infiltration of copper oxide was also investigated.
The powders were synthetized by a glycine/nitrate combustion process under a control of pH value in the nitrate solution. The combustion ashes were collected and subjected to calcination at different temperatures to find out best crystals of the related phases according to X-ray diffraction (XRD) patterns. Surface morphology of the powders was examined by scanning electron microscope (SEM). All powders were pressed in two different molds and sintered at 1100°C to make samples for measurement of their ohmic resistance and thermal expansion behavior. Each kind of Ba_(1-x) Ca_x Co_0.2 Fe_0.8 O_(3-δ) powders was mixed with the binder to make a paste. Then the paste was screen-painted on one side of an electrolyte (i.e., 〖Ba Ce〗_0.8 Zr_0.1 Y_0.1 O_3) and the Pt-paste on other side of it to make a single cell. The power density and electrochemical impedance spectroscopy (EIS) for the single cell of Pt/〖Ba Ce〗_0.8 Zr_0.1 Y_0.1 O_3/Ba_(1-x) Ca_x Co_(0"." 2) Fe_0.8 O_(3-δ), and for that of Pt/〖Ba Ce〗_0.8 Zr_0.1 Y_0.1 O_3/Ba_0.3 Ca_0.7 Co_(0"." 2) Fe_0.8 O_(3-δ) infiltrated with CuO were tested at 800°C. The flow rates of air inlet on cathode was at 200 c.c./min and that of hydrogen on anode at 450 c.c./min.
The results indicated that the power density of the cell increased with increasing the calcium content from x=0.5 to x=0.7 in the cathode made from Ba_(1-x) Ca_x Co_0.2 Fe_0.8 O_(3-δ). Copper oxide particles (CuO) infiltration (with mass ratio CuO/Ba_0.3 Ca_0.7 Co_(0"." 2) Fe_0.8 O_(3-δ) =1/1) does not have any significant effect on power density and increased polarization resistance.