Sol–gel synthesis of La0.6Sr0.4CoO3−x and Sm0.5Sr0.5CoO3−x cathode nanopowders for solid oxide fuel cells

Nano-powders of La0.6Sr0.4CoO3−x (LSC) and Sm0.5Sr0.5CoO3−x (SSC) compositions, which are being investigated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) with La(Sr)Ga(Mg)O3−x (LSGM) as the electrolyte, were synthesized by low-temperature sol–gel method using metal nitrates and citric acid. Thermal decomposition of the citrate gels was followed by simultaneous DSC/TGA methods. Development of phases in the gels, on heat treatments at various temperatures, was monitored by X-ray diffraction. Sol–gel powders calcined at 550–1000 °C consisted of a number of phases. Single perovskite phase La0.6Sr0.4CoO3−x or Sm0.5Sr0.5CoO3−x powders were obtained at 1200 °C and 1300 °C, respectively. Morphological analysis of the powders calcined at various temperatures was done by scanning electron microscopy. The average crystallite size of the powders was ∼15 nm after 700 °C calcinations and slowly increased to 70–100 nm after heat treatments at 1300–1400 °C.