PROPERTIES OF LA0.6SR0.4CO0.2FE0.8O3-X (LSCF) DOUBLE-LAYER CATHODES ON GADOLINIUM-DOPED CERIUM OXIDE (CGO) ELECTROLYTES - II - ROLE OF OXYGEN-EXCHANGE AND DIFFUSION

The area specific resistivity (ASR) of La0.6Sr0.4Co0.2Fe0.8O3-x cathod es on Gd-doped ceria electrolytes has been measured over the temperatu re range 325-725 degrees C, The ASR values for single layer porous cat hodes could be satisfactorily interpreted in terms of available data f or oxygen surface exchange coefficients. By introducing a thin (simila r to 1 mu m) dense layer of La0.6Sr0.4Co0.2Fe0.8O3-x (LSCF) adjacent t o the gadolinium-doped cerium oxide (CGO) electrolyte the resistivity values were decreased by a factor of 2-3 times; which could be explain ed by increasing the effective interfacial contact area between the LS CF and GGO. However calculations using data for oxygen self diffusion coefficients indicated much higher ASR values than determined experime ntally for these duplex layer cathode structures. It is necessary, the refore, to invoke enhanced oxygen ion transport through the dense laye r which could arise either due to the development of A-site deficient LSCF material, or too rapid diffusion via grain boundaries.