GDC-Infiltrated La0.3Ca0.7Fe0.7Cr0.3O3-δ Symmetrical Oxygen Electrodes for Reversible SOFCs
Because of the excellent performance of LSFC  as an air electrode, efforts are now focussed on further improving its performance in air and also in fuel environments. For this reason, the A-site of the perovskite was doped with Ca in place of Sr, primarily to decrease the thermal expansion coefficient of the perovskite to more closely match that of the most commonly used electrolytes . Although relatively low electrode polarization resistances were obtained with porous LSFCr  and LCFCr  electrodes, further improvement of the electrochemical performance would still be possible through microstructural modifications. Since the electrochemical performance of these mixed electronic and ionic conductors (MIECs) depends on the double phase boundary (DPB) area of the MIEC/electrolyte interface, in this study, an attempt was made to further enhance the DPB area by infiltrating the porous MIEC electrode with the electrolyte material (Gadolinia doped Ceria, GDC). To achieve this goal, a polymeric GDC solution precursor, which has the ability to form an interconnected film , was infiltrated into a previously sintered porous La0.3M0.7Fe0.7Cr0.3O3-δ scaffold structure.
Two types of electrolyte supported symmetrical cells were used in this study. In Type 1, LSFCr and LCFCr were screen-printed on both sides of a 250 µm thick GDC electrolyte-support, followed by firing at 1100 oC in air. A second set of cells was then infiltrated with a polymeric GDC precursor (Type 2).The performance of these half cells, operated at 600-800 oC in air, was then investigated. The initial impedance spectroscopy results showed that GDC infiltration resulted in a ca. 3 fold decrease in the polarization resistance of the MIEC electrodes in air at 800 °C. The 0.06 Ω.cm2 polarization resistance obtained for these electrodes at this temperature is a strong indication that polymeric GDC precursor infiltration into MIEC electrodes is a promising approach for the fabrication of very high performance RSOFC electrodes.
Acknowledgements: We are very grateful to the SOFC Canada NSERC Strategic Research Network, as well as Carbon Management Canada, for the support of this work. .
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