SYNTHESIS AND CHARACTERIZATION OF CaxLa1-xMnO3 COTHODS FOR APPLICATION IN CCOS

In this work, CaxLa1-xMnO3 cathodes were obtained and characterized for their application in CCSO. For this purpose, the cathode materials, CaxLa1-xMnO3, were synthesized by mechanosynthesis of stoichiometric mixtures of metal oxides: La2O3, CaO and Mn2O3, varying x from 0 to 1, in 0.1 intervals. The mechanosynthesis was carried out with a SPEX 8000D mill, grinding during different time intervals at room temperature, in an oxidizing atmosphere and using a 10:1 powder:powder weight ratio. X-Ray Diffraction was used to follow the synthesis process and to evaluate the effect of doping level and grinding time on the crystalline structure. Thermal analysis was used to determine the compositions with the highest thermal stability. Mixtures of Ca0.3La0.7MnO3 powders with different proportions of the lubricant (10, 15 and 20% by weight) were compacted at 200 MPa in a hydraulic press and sintering was performed by modifying the sintering conditions: time and temperature, in order to obtain cathodes for CCOS. The porosity and conductivity of the cathodes were determined as a function of working temperature, using a GWINSTEK GOM-802 direct current milli-ohm-meter. The structure and time required for the syntheses depended on the value of x, but after 7 h all were synthesized independently of x. Network parameters as a function of x were quantified. The most stable compositions are those with doping levels (x) between 0.4 and 0.6, The compacts sintered for 3 hours at 1100, 1200 and 1300C with 10% lubricant, achieve acceptable electrical conductivities at temperatures close to 400C, but increasing the sintering time generates a decrease in the number of pores,The sintered compacts that would perform best as cathodes in solid oxide fuel cells are those where 10% lubricant was incorporated and sintered at a temperature of 1100C for one hour.