Crystal structure, microstructure, electrical conductivity and electrochemical performance of a new family of iron perovskites with the general formula Ln0.5M0.5FeO3-δ (Ln = La and/or Pr; M = Sr, Ca or/and Ba) has been studied as function of mean A cation radius 〈rA〉. All the samples have a rhombohedral structure (space group: R-3c). SEM images show that the average grain size decreases with increasing 〈rA〉. The DC four-probe measurements indicate that all samples have high electrical conductivity, increasing with 〈r A〉. The electrochemical behaviour of these cathode materials was evaluated by using I-V curve measurements and AC impedance spectroscopy over three electrodes electrolyte supported cells. The results show a great improvement in cathode performance and a significant decrease in polarization resistance with increasing mean A cation radius 〈rA〉. ©The Electrochemical Society.