Sol-gel synthesis of La_(0.6)Sr_(0.4)CoO_(3_x) and Sm_(0.5)Sr_(0.5)CoO_(3-x) cathode nanopowders for solid oxide fuel cells

摘要

Nano-powders of La_(0.6)Sr_(0.4)CoO_(3_x) (LSC) and Sm_(0.5)Sr_(0.5)CoO_(3-x) (SSC) compositions, which are being investigated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOFCs) with La(Sr)Ga(Mg)O_(3-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 La_(0.6)Sr_(0.4)CoO_(3_x) or Sm_(0.5)Sr_(0.5)CoO_(3-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.