Perovskite Co-free La0.6Sr0.4M0.2Fe0.8O3−δ (M = Cr or Ti) mixed-conductors: Preparation and characterization

The new Co-free La0.6Sr0.4M0.2Fe0.8O3−δ (M = Cr or Ti) perovskite oxides have been successfully synthesized by the citrate acid complexing method. The La0.6Sr0.4Co0.2Fe0.8O3−δ and as-synthesized Co-substituted La0.6Sr0.4M0.2Fe0.8O3−δ (M = Cr or Ti) oxides all possess the rhombohedral perovskite-type structure. The structural stability, chemical reduction-tolerance ability (in a flowing 10% H2/helium stream) and sintering performance of the as-synthesized La0.6Sr0.4M0.2Fe0.8O3−δ (M = Cr or Ti) oxides were studied by XRD, TGA/DSC and SEM. The results demonstrate the reduction-tolerance ability of the as-synthesized Co-free La0.6Sr0.4M0.2Fe0.8O3−δ (M = Cr or Ti) oxides is improved significantly compared to that of the Co-containing La0.6Sr0.4M0.2Fe0.8O3−δ (M = Co) oxide. The presence of Cr3+/4+ or Ti3+/4+ ions in the B-sites of the perovskite-type structure can further stabilize the neighboring oxygen octahedral (BO6) due to the stronger columbic attraction, leading to the enhanced stability of the as-synthesized Cr- or Ti-substituting perovskite Co-free oxides.