SYNTHESIS AND CHARACTERIZATION OF STRONTIUM AND IRON-DOPED LANTHANUM COBALTITE NANOCRYSTALLINE POWDERS FOR SINGLE CHAMBER SOLID OXIDE FUEL CELLS

摘要

Different sets of perovskite-type oxides of general formula La_(0.8)Sr_(0.2)Co_(1-x) Fe_xO_3 (0.0 < x < 1.0) were successfully prepared by the amorphous citrate method. Simultaneous thermogravimetric and differential thermal analysis (TG-DTA) was carried out on the precursor gels to determine the minimum temperature of the oxide formation, which was found to be 600℃. After thermal treatments, samples were characterized by using Induced Couple Plasma (ICP) spectroscopy, X-ray diffraction (XRD) and Scanning Electron Microscope (SEM). Single-phase nanocrystalline powders were obtained with controllable grain size from 10 to 20 nm as a function of the iron ratio. ICP results indicate that for the prepared samples the actual metal contents were nearly equal to the nominal values. XRD results showed that La_(0.8)Sr_(0.2)Co_(1-x)Fe_xO_3 compounds possess a rhombohedral to orthorhombic structure, depending on the iron content. Moreover, the perovskite-type nano-powder oxides were characterized as electrodes on Ce_(0.8)Sm_(0.2)O_(2-x) pellets in symmetrical cells, and the electrochemical properties of the electrode/electrolyte interfaces were investigated using electrochemical impedance spectroscopy (EIS).