Effects of Strontium Doping on Oxygen Reduction Kinetics in La1-xSrxCo0.2Fe0.8O3-δ Cathodes
Committee Members: Advisor: Professor Srikanth Gopalan, MSE/ME; Professor Soumendra N. Basu, MSE/ME; Professor Uday. B. Pal, MSE/ME
Abstract: Dense films of the mixed ionic-electronic conductor lanthanum strontium cobalt ferrite (La1-xSrxCo0.2Fe0.8O3-δ) with x= 0.4, 0.3 and 0.2 (thereafter referred to as LSCF-6428, LSCF-7328 and LSCF-8228) were deposited in fixed patterns on yttria-stabilized zirconia (YSZ) substrates on top of a gadolinium-doped ceria (GDC) barrier layer by pulsed laser deposition (PLD) at the Pacific Northwest National Laboratory (PNNL) in Richland, WA. Electrochemical impedance spectroscopy (EIS) data were gathered for each of the compositions at atmospheric pressure, but at varying temperatures (600, 700 and 800 °C). The total electrode polarization resistance, Rpol, was plotted as a function of composition and temperature. Results show that, for all temperatures, total polarization resistance drops considerably when the Sr composition is reduced from 0.4 to 0.3, and then increases slightly as the Sr composition is further reduced from 0.3 to 0.2 The relatively high polarization resistance for LSCF-6428 supports recent evidence found by other members of our research group of surface strontium migration in LSCF-6428 films, which results in the formation of an insulating strontium oxide phase.