Structure, chemical stability and electrical conductivity of perovskite La0.6Sr0.4M0.3Fe0.7O3−δ (M = Co, Ti) oxides

The perovskite La0.6Sr0.4M0.3Fe0.7O3−δ (M = Co, Ti) powders have been synthesized by the citrate gel method. The structural and chemical stability of the La0.6Sr0.4M0.3Fe0.7O3−δ (M = Co, Ti) oxides were studied by X-ray diffraction (XRD), differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) techniques. The electrical conductivities of the sintered La0.6Sr0.4M0.3Fe0.7O3−δ (M = Co, Ti) ceramics were measured. The results demonstrate the chemical stability in H2/helium (He) atmosphere of the La0.6Sr0.4Ti0.3Fe0.7O3−δ oxide is improved significantly compared to that of the La0.6Sr0.4Co0.3Fe0.7O3−δ oxide. The incorporation of Ti3+/4+ ions in the perovskite structure can significantly stabilize the neighboring oxygen octahedral due to the stronger bonding strength, leading to the enhanced structural and chemical stability of the La0.6Sr0.4Ti0.3Fe0.7O3−δ. In addition, the perovskite La0.6Sr0.4M0.3Fe0.7O3−δ (M = Co, Ti) oxides possess much higher chemical stability in CO2/He atmosphere than that of Ba0.5Sr0.5Co0.8Fe0.2O3−δ oxide, in which the perovskite structure is destroyed completely in a flowing CO2-containing atmosphere.