Performance of (Ln_(0.5)M_(0.5))FeO_(3-δ)??Perovskites as Cathode for SOFCs:Effect of Mean Radius of the A Site Cations

摘要

Crystal structure, microstructure, electrical conductivity andelectrochemical performance of a new family of iron perovskiteswith the general formula Ln_(0.5)M_(0.5)FeO_(3-δ)?(Ln = La and/or Pr; M =Sr, Ca or/and Ba) has been studied as function of mean A cationradius . All the samples have a rhombohedral structure (spacegroup: R-3c). SEM images show that the average grain sizedecreases with increasing . The DC four-probe measurementsindicate that all samples have high electrical conductivity,increasing with . The electrochemical behaviour of thesecathode materials was evaluated by using I-V curve measurementsand AC impedance spectroscopy over three electrodes electrolytesupported cells. The results show a great improvement in cathodeperformance and a significant decrease in polarization resistancewith increasing mean A cation radius .