Preparation and Characterization of Pr‐Sr‐Co‐Fe‐Al‐O Based Perovskite Oxides for SOFC Cathodes

The influence of up to 40 mol% Al substitution for Fe on the properties of the perovskite oxides (Pr1-xSrx)(Co0.2Fe0.8)O3-δ (x = 0.1, 0.3) was studied. The oxides were prepared by citrate synthesis and characterized by X-ray diffraction, dilatometry and 4-point DC. The above oxides had an orthorhombic perovskite structure, with the exception of (Pr0.7Sr0.3)(Co0.2Fe0.4Al0.4)O3-δ, which had the cubic structure. The lattice parameters were determined from the room temperature XRD data, using the LSUCR computer program. In general the unit cell volume decreased with increasing Al content, due to the larger size of Al3+ cation compared to that of Fe3+. The linear thermal expansion coefficient (TEC) at 700°C decreased as Al content increased. The electrical conductivity decreased with increasing Al content. From the above oxides, (Pr0.7Sr0.3)(Co0.2Fe0.6Al0.2)O3-δ, with proper tailoring of composition, seems to be the most suitable material for use as SOFC cathode. Its TEC value was 14.5 × 10−6 cm (cm °C)−1, while its electrical conductivity had a value of 80 S cm−1 at 700 °C.