Effect of Cathodic Polarization on the La0.6Sr0.4Co0.2Fe0.8O3-δ-Cathode/Gd-Doped Ceria-Interlayer/YSZ Electrolyte Interfaces of Solid Oxide Fuel Cells.

Evaluation of the interfaces is critical for improved long-term stability and performance of solid oxide fuel cells (SOFC) under required operating conditions. In this work, cells consisting of LSCF-cathode|GDC-interlayer|8YSZ-electrolyte|Pt-anode were tested under open-circuit voltage (OCV) and cathodic polarization at a constant current of -0.3 A at 800°C for 300 h in air. Dense GDC films by pulsed laser deposition (PLD) were used as reaction barrier layers. The results showed that after cell tests, SrZrO₃ formed at the LSCF/GDC interface in consequence of the fast Zr migration in the PLD-grown GDC interlayers. However, SrZrO₃ formation and GDC microstructural feature differ between OCV and cathodic polarization. Under OCV, SrZrO₃ laterally formed at the O₂/LSCF/GDC triple phase boundary with GDC interlayer showing increased porosity near the YSZ electrolyte. Both of these led to a drastic increase in polarization resistance with time. Under cathodic polarization, localized transverse growth of SrZrO₃ was observed, and an apparent pore elimination occurred in GDC. Cells also showed no performance degradation under cathodic polarization. Based on the above observation, a plausible cation diffusion behavior and oxygen transport is discussed. [ABSTRACT FROM AUTHOR]