Characterisation of La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) and Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ) as Cathode Materials for the Application in Intermediate Temperature Fuel Cells

摘要

Capable materials for solid oxide fuel cell cathodes have to provide high electrocatalytic activity for oxygen reduction as well as sufficient electronic conductivity and good ionic transport properties (1). This study compares the electrical transport properties and the oxygen exchange properties of two promising cathode materials for operating temperatures between 600 and 800°C: La_(0.6)Sr_(0.4)Co_(0.2)Fe_(0.8)O_(3-δ) and Ba_(0.5)Sr_(0.5)Co_(0.8)Fe_(0.2)O_(3-δ). Both materials were synthesized by spray pyrolysis and characterised with respect to phase purity and to the element ratio by XRD and ICP-AES analysis. The sintering behaviour of the calcined powders and the coefficients of thermal expansion of dense sintered samples were studied by dilatometry. As important parameters for the oxygen exchange reaction the chemical surface exchange coefficients (k ) and chemical diffusion coefficients (D) as well as the electrical conductivities are compared.