La0.6Sr0.4Co0.2Fe0.8O3 perovskite cathode for intermediate temperature solid oxide fuel cells: A comparative study

In this study the characteristics of two different kinds of La0.6Sr0.4Co0.2Fe0.8O3 (LSCF) powders, one in-house powder synthesized by a co-precipitation method and another purchased from the Fuel Cell Materials Co. (FCM Co., USA) were compared. The co-precipitated powder was prepared by using ammonium carbonate as the precipitant with a NH4+/NO3- molar ratio of 2 and calcination at 1000?C for 1 h. Phase composition, morphology and particle size distribution of powders were systematically studied using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and laser particle size analysis (LPSA), respectively. The synthesized and commercial LSCF powders were overlaid on an Yttria-stabilized zirconia (YSZ) electrolyte having a gadolinium-doped ceria (GDC) interlayer. Electrochemical Impedance Spectroscopy (EIS) measurements were carried out at various operating temperatures in the range of 600-850?C. XRD and FESEM analysis revealed that single phase nano-crystalline LSCF powder with a mean crystallite size of 14 nm and mean particle size of 90 nm was obtained after calcination at 1000?C. The presence of hard agglomerated particles larger than a few microns in the commercial powder and also sub-micron agglomerates in the co-precipitated LSCF powder might be related to the final mechanical milling process and high calcination temperature of powders, respectively. LPSA results showed an identical mean particle size of about 1.5?m for both LSCF powders. EIS results revealed almost identical polarization resistance for both LSCF powders.