Synthesis and Characterization of Nanocrystalline La0.65Sr0.3 MnO3 and La0.8Sr0.2MnO3 Cathode Powders by Auto-ignition Technique for Solid Oxide Fuel Cells (SOFC)
Solid Oxide fuel Cells (SOFCs) are considered to be one of the most promising energy conversion devices that have several advantages such as high efficiency, system compactness and low environmental pollution. In the present investigation La0.65Sr0.3MnO3 (LSM-1) and La0.8Sr0.2MnO3 (LSM-2) nanoceramic powders were prepared by citrate-nitrate route of auto-combustion with citrate to nitrate (c/n) ratio 0.50 to see the effect of these cathode powders on the performance of SOFC cells. The as prepared powder were calcined at 900oC for 4hrs using the Thermolyne 47900 furnace to remove carboneous residues and characterized them using SEM / EDS, XRD, TGA techniques and their results are presented . From calculations using Debye Scherrer’s equation, the average crystallite size of the powders were found to be around 16nm. The SEM indicates the particle sizes are within the range of around 200nm.The surface area of the calcined LSM-2 powder was found to be ~21m2/g. The TGA studies indicate the completion of combustion since there was no further weight loss after reaching temperature of ~ 650oC.
Also, Electrochemical characterization of LSM cathode powders were carried out by coating these powders (as cathode functional layer CFL-Bottom and current collector layer CL- Top) using Screen printing on the SOFC half cells (NiO-YSZ+YSZ) procured from CGCRI, Kolkata, India with a cell size of 16mm dia x1.6mm and tested these cells with H2-O2 at 750-800oC with the flow rates of 100-200 sccm. The results of the performances of single cells are presented in this paper. The Current density and powder density values obtained are 0.80A/cm2 (at 0.7V) and 0.55 W/cm2 at 800oC with 200 sccm of hydrogen and oxygen respectively. The area surface resistance (ASR) values obtained were ~0.50 Ωcm2 at 0.7V at 800oC.
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