Copper Doped La0.8Sr1.2FeO4 Ruddlesden-Popper SOFC Cathode: Synthesis, Characterization and Model Analysis

Novel La0.8Sr1.2Fe0.9Cu0.1O4±δ (LSFC) oxides for application as cathodes in SOFCs were prepared with two different synthetic methods: solid-state-reaction (SSR) and molten citrate (MC). The XRD, ICP-OES, SEM, laser granulometry and TG-DTA techniques were applied for the physico-chemical characterization. 4-points DC conductivity measurements and EIS experiments were performed in the electrochemical characterization. Compared to SSR, the MC method allowed to obtain finer powders (∼2 μm vs. ∼5 μm) and required lower calcination temperatures (1,000 °C vs. 1,400 °C). The SSR and MC samples showed similar conductivity (30 S cm−1 at 700 °C) and polarization resistance (1.7 Ω cm2 at 700 °C). The EIS results were analyzed with the equivalent circuits method, and with a physically-based model for the simulation of the impedance spectra, which indicated that the oxygen reduction mechanism involved the TPB. The MC method revealed preferential, thanks to the lower calcination temperature.