Synthesis And Electrical Properties Of LSCF Composite Cathode For IT-SOFC Applications

(La_0.6Sr_0.4)_0.99Co_0.2Fe_0.8O₃-??LSCF?is regarded as a promising cathode material for intermediate temperature solid oxide fuel cells due to its excellent ionic and electronic conductivities at 600-700 °C.In this work,LSCF submicron powders with low agglomerate are synthesized by a solid liquid composite method,and the resultant powders are characterized by XRD,XRF,SEM,LPSA and BET.The perovskite phase of LSCF forms completely after 850 °C calcining.It is shown that via the solid liquid composite method,uniform and well dispersed spherical LSCF submicron powders are synthesized,with the mean particle size of about 200 nm.In addition,the synthesis yield of the LSCF powders was reach 5 kg per batch by the solid liquid composite method,which is conform to the commercial development trend of solid oxide fuel cells.However,LSCF is not compatible with the stabilized zirconia electrolyte materials(e.g.,?Y₂O₃?0.08?ZrO₂?_0.9)2,8YSZ,?Sc₂O₃?_0.1?CeO₂?_0.01?ZrO₂?_0.89,10Sc)1CeSZ),because the cathode layer often deteriorates the cell performance owing to the formation of highly resistive second phases such as Sr ZrO₃ at the interface between stabilized zirconia electrolyte and cathode layers during high-temperature sintering??800 °C?.To prevent these reactions from occurring,a thin DDC?D doped ceria,D = Gd,Sm?interlayeris often coated onto the stabilized zirconia electrolyteIn this paper,four types of doped ceria powders and sinters,including Gd_0.1Ce_0.9O_1.95,Gd_0.2Ce_0.8O_1.9,Sm_0.1Ce_0.9O_1.95 and Sm_0.2Ce_0.8O_1.9,are prepared and characterized.The results indicate that the Sm_0.2Ce_0.8O_1.9 samples possess the lowest densification temperature and a relatively optimal conductivity,which make it more suitable for use as an interlayer compared to other doped ceria.In addition,a series of interlayers were prepared from Sm_0.2Ce_0.8O_1.9 powders with different precalcination temperatures using an industrial screen printing method.The area-specific resistances of these interlayers were determined from their microstructures,including the grain and pore size,electrolyte/interlayer interface,layer uniformity and density,which are significantly dependent on the precalcination temperatures of the powders.A minimum area-specific resistance of 0.036?·cm²at 750 °C was obtained for the sample withSm_0.2Ce_0.8O_1.9 powders precalcined at 950 °C?the corresponding BET value was approximately20 m²g-1?.In addition,lanthanum strontium cobalt ferrite?LSCF?cells were prepared with the as-preparedSm_0.2Ce_0.8O_1.9 interlayer.Their power density was measured and determined to be 0.72 Wcm^-2at 750 °C?0.75 V,active area of 64 cm²?.