Synthesis and electrochemical properties of Sr3 Fe1.8 Co0.2 O7 as a solid oxide fuel cell cathode

Solid oxide fuel cells (SOFCs) have attracted a lot of attention for their high efficiency, fuel flexibility, lower air pollution, etc. Unfortunately, their operating high temperature is the main shortcoming for commercialization. One of the main hurdles to achieving intermediate temperature SOFCs is the conductivity of their cathode materials at lower temperatures. Therefore, in this study, a conductive Sr3 Fe1.8 Co0.2 O7 cathode material with a Ruddlesden−Popper crystal structure was first successfully synthesized, and then the effect of sintering temperature was investigated. X-ray diffraction analysis results revealed that the powder was approximately pure. Moreover, field emission scanning electron microscope (FESEM) micrographs showed rod-shaped particles with an average particle size of 670 nm. To evaluate the sintering effect on the electrochemical behavior of the synthesized powder, a paste of the powder was painted on both sides of a Gadolinium doped Ceria (CGO) electrolyte and sintered at 1000°C and 1100°C. The electrochemical impedance analysis on symmetrical half-cells revealed that the minimum polarization resistance for the sintered cathode at 1000°C and 1100°C was 1.1 Ω.cm2 and 1.6 Ω.cm2 at 800C֯. The FESEM micrograph showed High-temperature sintering could affect the interface between CGO and SFCO and decrease transport pathways for oxygen ions conduction at higher sintering temperatures. Also, the electrical conductivity of the sample was determined by the four-point probe electrical conductivity method in the temperature range of 200-800˚C at room atmosphere. The results show that the maximum electrical conductivity at 427°C is 76 S.cm-1.