Thesis (M.Sc.)--Chulalongkorn University, 2013

The composites of (Ba0.5Sr0.5)0.7Ca0.3Co0.8Fe0.2O3−d (BSCCF) with YSZ and GDC electrolytes in 1:3, 1:1 and 3:1 weight ratio were investigated at 850 – 1300 °C. Phase structures were characterized by XRD. Sr(ZrO3), SrCoO3 and CaZrO3 were obtained after firing the BSCCF:YSC composites at 850 -1300 °C for 7-10 hrs, on the contary no other phases were observed when the BSCCF:GDC composites were fired at 850 °C. The electrical conductivity and the oxygen permeation of both composites were lower than (Ba0.5Sr0.5)0.7Ca0.3Co0.8Fe0.2O3−d. The internal resistance of symmetric cell and the single cell performance of (Ba0.5Sr0.5)0.7Ca0.3Co0.8Fe0.2O3−d and composites were performed at 850 – 650 °C. It was found that the symmetric cell of (Ba0.5Sr0.5)0.7Ca0.3Co0.8Fe0.2O3−d fabricated with the GDC interlayer showed the lowest interfacial resistance at 850 °C. And, the highest single cell performance was obtained from (Ba0.5Sr0.5)0.7Ca0.3Co0.8Fe0.2O3−d with the GDC interlayer as 163.84 mW/cm2 at 850 °C. Surface morphology and cross section images of cathodes after the single cell performance indicated no transformation of cathode along the interface on the single cell coated with GDC interlayer.