CHARACTERIZATION OF La0.6Sr0.4Co0.2Fe0.8O3 CATHODE POWDERS PREPARED VIA ACTIVATED CARBON-ASSISTED SOL-GEL METHOD

Abstract

In this study, the La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) cathode powders were prepared by an activated carbon-assisted sol-gel method. The activated carbon was used as a dispersing agent to produce well-dispersed particle and improve the microstructure of the cathode powders. The powders were calcined in air at the temperature range of 400 to 1100 oC. The characterizations of the resultant powders were performed by using X-ray diffractometer (XRD), field emission-scanning electron microscopy (FESEM), Brunauer-Emmett-Teller (BET) analysis and impedance spectroscopy. Single perovskite phase of LSCF was completely formed at 700 oC and preserved even after calcination temperature of 1100 oC. As confirmed by BET analysis, a higher surface area was obtained for powder sample prepared with the aid of the dispersing agent, which is 11.02 m2g-1 . The FESEM images confirm a good contact of the cathode and electrolyte layer. The electrochemical measurement of LSCF symmetrical cell at 750 o was performed and evaluated. The impedance spectra obtained were resolved by a fitting procedure using an equivalent circuit that consists of a combination of four parallel pairs of resistor-constant phase element (R-CPE) in series. The different impedance arc were allocated to the corresponding processes using the capacitance (C) value related to each arc. Grain boundary response, interfacial processes and cathode reactions were respectively assigned by their associated capacitance value which is C≈10-10, C≈10-7, and C≈10-3 F.