Thin film YSZ coatings on functionally graded freeze cast NiO/YSZ SOFC anode supports

Intermediate temperature (600–800 °C) solid oxide fuel cell (SOFC) technology is often limited by inadequate gas transport in electrodes, and high ion transport resistance electrolytes. In this study, large area filtered arc deposition (LAFAD) and hybrid filtered arc-assisted e-beam physical vapor deposition (FA-EBPVD) technologies, in combination with freeze-tape-casting, were used to fabricate SOFC anode/electrolyte bi-layers with functionally graded porous anode microstructures and thin film electrolytes favorable for both gas transport and low resistance. Traditionally-processed NiO/YSZ in addition to freeze-tape-cast NiO/YSZ anode substrates were fabricated and subsequently coated with thin film (<1–20 μm) YSZ via LAFAD and FA-EBPVD. LAFAD was found to be effective in applying thin (~1 μm) dense YSZ films on porous substrates at ~400 °C. FA-EBPVD produced relatively thick (~10–20 μm) dense YSZ coatings on porous substrates, with columnar morphology and nano-metrical grain size. A ~10 μm FA-EBPVD YSZ coating was observed to bridge NiO/YSZ surface pores of ~10 μm, which typically requires pre-filling prior to conventional thin film coating processes. Coated substrates exhibited negligible curvature, yielding flat anode/electrode bi-layers up to 2.5 cm in diameter. These results are presented with conderations for future SOFC development discussed.