Study on Structural Refinement and Electrochemical Behaviour of Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) as Cathode Materials for Intermediate Temperature Solid Oxide Fuel Cells (IT-SOFC)

摘要

Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) (BSCF) was prepared by ethylene glycol-citrate combined sol-gel combustion route and calcined at optimized temperature 1050°C. The X-ray Diffraction (XRD) data revealing the crystal purity of BSCF cathode was refined by the Cubic-type structure having the space group Pm-3m by Rietveld analysis. Refined lattice parameter of BSCF cathode is a=3.9759 A and unit cell volume is 62.85 (4) A~3, Co/Fe-O bond length from VESTA program figured out to be 1.987 (3) A. Electron density distribution (EDD) of the unit cell of BSCF cathode shows the bonding feature with oxygen ions, this could represent oxygen vacancies are present in the lattice. These results reflected in electrochemical impedance spectra measurement of symmetric cell. Area of specific resistance (ASR) of the BSCF cathode was found to be 0.17 Ω.cm~2 at 700°C and respective activation energy (Ea) 1.15 eV. It shows surface exchange at cathode interface, surface diffusion and self-diffusion happened through Ce_(0.85)Sd_(0.15)O_(1.95) (SDC15) electrolyte.