PREPARATION AND CHARACTERIZATION OF • NANOSTRUCTURED ELECTRODES OF SOLID OXIDE FUEL CELLS

Abstract

In order to develop intermediate temperature solid oxide fuel cell with low cost and enhanced durability, optimization is must in selection of materials, synthesis of powders and & fabrication of cell. In the present study nanoparticles ofNio.75Feo.2501125 and Gdo.lCeo901.95 were successfully prepared via sd-gel process and Lao60Sro40Co0.2oFeo8003 were synthesized via polymeric-complexing process. Furthermore, Nio.75Feo.2501.I25 and Gdo.ICeo.901.95 composite anode and Lao60Sro40Co0.2oFeo.8003 cathode pellets were fabricated via conventional uni-axial dry pressing and solid state sintering. Synthesized powders were characterized using X-ray di ffractometer, transmission electron microscopy, field emission scanning electron microscopy and thermo-gravimetric and differential thermal analysis for analyzing phase transformation and composition, crystal structure, particle size and morphology. Sintered pellets were characterized using field emission scanning electron microscopy, energy dispersive spectroscopy, Archimedes method and Keithley multimeter for investigating particle size, morphology, composition, densification and temperature dependent electrical conductivity properties. Crystalline cubic fluorite phase Gdo.ICeo.901.95 nano-powder with particle size of 30-50 nm and NiO cubic phase and NiFe204 cubic-spinel phase with 40-60 nm particle size in Nio75Feo.2501.125 were observed. Also the irregular non-spherical shaped morphology and polycrystalline nature were observed in both the powders. Lao60Sro 4oCoo.2oFeo.8003 nano-powder showed cubic perovskite phase along with nano-rod like morphology with 20 nm of diameter and 80 nm of length average with citric acid as chelating agent and nano-sphere like morphology with 50 nm of diameter average with mixture of citric acid and ethylenediarninetetraacetic acid as chelating agent. Electric conductivity measured at 800 °C for composite anode pellets sintered at 1200. 1250. 1300 and 1400 °C were 0.0075, 0.0278, 0.0396, 0.048 S/cm, respectively and for cathode pellets sintered at 900, 950 and 1000°C with citric acid as chelating agent were 0.144, 0.217 and 0.265 S/cm, respectively and with mixture of citric acid and ethylenediaminetetraacetic acid as I iii chelating agent were 0.137, 0.209 and 0.249 S/cm, respectively. Electrical conductivity of both composite anode and cathode pellets increases with increase in both operational and sintering A. temperature, similar to usual semiconductor behavior of mixed ionic and electronic conductor. Heterogeneous mixed ionic and electronic conductor like phase formation was confirmed by scanning electron microscopy images derived from backscattered electrons of composite anodes.