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Porous and about 40-μm-thick LNF cathodes were deposited on both sides of the substrate and sintered at 1100°C. Different thicknesses of the thin perovskite layer were investigated in order to find the most effective one and to better understand its influence on the cathode/electrolyte interface. It was found that approximately 150 nm LNF or LSCF layer is sufficient to minimize interface resistance and improve cathode reproducibility. It was concluded that the thin perovskite layer increases contact area and improves the oxygen ion transport between the cathode and electrolyte without influencing the oxygen reduction reaction mechanism.

Recently, it was shown that thin functional layers introduced between an electrolyte and cathode might improve cathode performance. However, the mechanism of this improvement still needs analysis. In this paper, a thin (~140 nm), spin-coated perovskite layer (La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ) was placed between a cathode (La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ) and an electrolyte (Ce 0.8 Gd 0.2 O 2-δ) and the effects of this investigated. The microstructure of this layer was varied in order to determine its impact on the electrical and electrochemical properties. It has been shown that a mesoporous, nanocrystalline layer increases the active area for oxygen reduction and charge transfer through the cathode/electrolyte interface, which improves performance. Moreover, the stability of the cathode from thermal stresses is increased. In contrast, the coarsening of the grain and the layer densification has a reduced impact on the cathode performance.

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