Facile autocombustion synthesis of La_0.6Sr_0.4Co_0.2Fe_0.8O_{3- δ} (LSCF) perovskite via a modified complexing sol-gel process with NH₄NO₃ as combustion aid

Ammonia nitrate was applied as an oxidizer and combustion trigger to modify the normal combined EDTA-citrate complexing method into a process with autocombustion and low ignition temperature properties. Therefore, the synthesis procedure was greatly simplified. The effect of NH₄NO₃/metal ions to organic mole ratios and the heating temperature on the autocombustion behavior and the properties of the powders derived were investigated in detail. The critical amount of NH₄NO₃ for the autocombustion to occur was identified at the NO₃^- to citric acid to EDTA mole ratio of around 10:2:1. After the experimental optimization, well-crystallized nanostructured La_0.6Sr_0.4Co_0.2Fe_0.8O_{3- δ} (LSCF) powder with a specific surface area as high as 21 m²/g was obtained; it is comparable with that obtained from a normal complexing process. By adjusting the combustion parameters, the properties of the powders then derived can be tailored for different applications, such as nanograined dense membrane for oxygen separation membrane, and porous cathode for fuel cells and sensors.