SrZrO₃Formation at the Interlayer/Electrolyte Interface during (La_1-xSr_x)_1-δCo_1-yFe_yO₃Cathode Sintering

Abstract

This work probes the formation of SrZrO<sub>3</sub> at the SDC/YSZ interface (Sm doped ceria, SDC; Y stabilized zirconia, YSZ) during (La<sub>1-x</sub>Sr<sub>x</sub>)<sub>1-δ</sub>Co1<sub>-y</sub>Fe<sub>y</sub>O<sub>3</sub> (LSCF) cathode sintering. SEM/EDS and grazing incidence X-ray diffraction results of annealed LSCF and YSZ samples reveal that even without physical contact between LSCF and YSZ, SrZrO<sub>3</sub> was formed on the surface of YSZ, preferentially at the grain boundaries. It was suspected that the SrZrO<sub>3</sub> formation is due to the Sr-containing gas species diffused through the pores of the SDC layer and reacted with the YSZ electrolyte. Computational thermodynamics was adopted to predict the gas species formed in air during sintering by using the La-Sr-Co-Fe-O-H thermodynamic database. Sr(OH)<sub>2</sub> is identified as the dominant Sr-containing gas species under the experimental conditions. In addition, it was found that A-site deficiency in LSCF could effectively suppress the SrZrO<sub>3</sub> formation while a dense and pore-free SDC interlayer is required to totally block the SrZrO<sub>3</sub> formation. As a result, cell performance was significantly improved for a cell with a dense SDC interlayer fabricated by pulsed laser deposition, due to elimination of SrZrO<sub>3</sub> formation and therefore reduced interfacial resistance.