Functionally graded cathodes for solid oxide fuel cells

Functionally graded Solid Oxide Fuel Cell cathodes have been prepared from mixtures of strontium doped lanthanum manganite (LSM) and yttria stabilised zirconia (YSZ) using screen printing techniques. Samples were characterised using scanning electron microscopy, elemental dot mapping, and electrochemical impedance spectroscopy. Characterisation using AC impedance techniques showed that each cathode could be analysed in terms of a low frequency, mid frequency and high frequency response. Results showed that as the level of YSZ-LSM grading within the cathode increased, the polarisation resistance decreased. No region of the graded cathode should contain less than 20 wt% LSM to prevent an accompanying increase in series resistance. (C) 2001 Kluwer Academic Publishers.