Synthesis and Characterization of La0.6Sr0.4Co0.8Fe0.2O3-δ(LSCF) Ultrafine Powders by the Sol-Gel and Self-Combustion Process

La(0.6)Sr(0.4)Co(0.8)Fe(0.2)O(3-delta) (LSCF) ultrafine powders were synthesized by the combined sol-gel and self-combustion method. The phase formation and the microstructure of the self-combustion yielded products were characterized by XRD, TG-DTA and TEM. The results showed that the powders were composed of a single phase of the perovskite structure with the particle size in the range of 30 nm and 70 nm. The powders were sintered at 1100 degrees C for 2 h to form the ceramic bodies with the relative density of 95%. The sintered material exhibited thermal expansion coefficient of 19.3x10(-6)/K from room temperature to 1000 degrees C. Its electrical conductivity, measured by four-probe method, showed an increase from 580 S.cm(-1) up to a maximum of 1000 S.cm(-1), as the temperature increased from 200 degrees C to about 600 C. This was followed by a slight decrease with the further increase of temperature. The high electrical conductivity above 500 S.cm(-1) from 200 to 800 degrees C is believed to satisfy well the technical requirements by the low and intermediate temperature SOFCs.