Synthesis of nano-crystalline (Ba0.5Sr0.5)Co0.8Fe0.2O3−δ cathode material by a novel sol–gel thermolysis process for IT-SOFCs

Nano-crystalline (Ba0.5Sr0.5)Co0.8Fe0.2O3−δ powder has been successfully synthesized by a novel sol–gel thermolysis method using a unique combination of PVA and urea. The decomposition and crystallization behaviour of the gel precursor was studied by TG/DTA analysis. The gel precursor was calcined at different temperatures and the phase evoluation was studied by X-ray diffraction (XRD) analysis. From the result of X-ray diffraction patterns, it is found that a cubic perovskite (Ba0.5Sr0.5)Co0.8Fe0.2O3−δ was formed by calcining the precursor at 450 ◦C for 5 h, but the well-crystalline cubic perovskite (Ba0.5Sr0.5)Co0.8Fe0.2O3−δ was obtained by calcining the precursor at 650 ◦C for 5 h. Morphological analysis of the powder calcined at various temperatures was done by scanning electron microscope (SEM). Thermogravimetric (TG) results showed the lattice oxygen loss of the product was about ∼2% in its original weight in the temperature range 40–900 ◦C. Finally, thermal expansion and electrical conductivity of the synthesized material were measured by dilatometer and four-probe dc method, respectively