Composite LSF-YSZ and LSCrF-YSZ Electrode Scaffolds for Infiltrated SOFC Cathodes

Tuesday, 25 July 2017: 10:20
Grand Ballroom West (The Diplomat Beach Resort)
Y. Cheng (University of Pennsylvania), T. S. Oh (Auburn University), M. Rahmanipour (Politecnico di Milano), R. Wilson, R. J. Gorte, and J. M. Vohs (University of Pennsylvania)
Conductive scaffolds were investigated for use in fabrication of SOFC cathodes in order to reduce the number of perovskite infiltration steps required to achieve sufficient conductivity. Initial work involved composites of Sr-doped LaFeO3 (LSF) and YSZ. Although no new phases form when LSF-YSZ composites are calcined to 1623 K, shifts in the lattice parameters indicate Zr can enter the perovskite phase. Measurements on dense, LSF-YSZ composites show that the level of Zr doping depends on the Sr:La ratio. Because conductivity of undoped LSF increases with Sr content but both the ionic and electronic conductivities of Zr-doped LSF decrease with the level of Zr in the perovskite phase, there is an optimum initial Sr content corresponding to La0.9Sr0.1FeO3 (LSF91). Although scaffolds made with 100% LSF had a higher conductivity than scaffolds made with 50:50 LSF-YSZ mixtures, the 50:50 mixture provided better interfacial structure with the electrolyte and sufficient conductivity, providing the better cathode performance upon infiltration of La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF). To minimize Zr doping, we also examined scaffold composites made from La0.8Sr0.2CrxFe1-zO3-δ (LSCrF) and YSZ. For intermediate Cr contents, it was possible to prevent Zr doping and maintain reasonable performance of cathodes made from LSCrF-YSZ composites.