Novel ln1-xcaxfe0.8ni0.2o3 (ln=la, pr; 0<x<1) phases with perovskite type structure as cathode materials for solid oxide fuel cells

Résumé

Perovskite-type oxides with the general formula ABO3 have been widely studied and are utilised in a large range of applications due to their tremendous versatility. In particular, the high stability of the perovskite structure compared to other crystal arrangements and its ability, given the correct selection of A and B cations, to maintain a large oxygen vacancy concentration makes it a good candidate as a cathode in Solid Oxide Fuel Cell (SOFC) applications. In this work several SOFC cathode materials are reported and their potential as electrodes discussed. The synthesis, structure, physicochemical and electrochemical properties of a series of transition metal perovskite oxides of general formula Ln1-xCaxFe0.8Ni0.2O3 where Ln = La, Pr and 0 menor x menor1 have been investigated. In the case of La0.6Ca0.4Fe0.8Ni0.2O3 and La0.6Sr0.2Ca0.2Fe0.8Ni0.2O3 cathodes, thin films were obtained by laser ablation and investigated by Electrochemical Impedance Spectroscopy. Finally, the optimisation of La0.6Ca0.4Fe0.8Ni0.2O3 (LCFN) as a cathode material was explored. In order to achieve this, three actions were taken. The first was to mix the LCFN with ionically conducting Ce0.8Sm0.2O2 (SDC) as a composite electrode. Secondly, several symmetric cells were produced using yttria stabilised zirconia (YSZ) as the electrolyte in order to investigate the effect of sintering temperature on microstructure and performance. Finally, in order to avoid reaction layer formation seen with YSZ, the use of a Ce0.8Gd0.2O2 (CGO) electrolyte was investigated.