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Reduced operating temperatures ͑600-800°C͒ of solid oxide fuel cells ͑SOFCs͒ may enable the use of inexpensive ferritic steels as interconnects. Due to the demanding SOFC interconnect operating environment, protective coatings are gaining attention to increase long-term stability. In this study, large area filtered arc deposition and hybrid filtered arc deposition-assisted electron beam physical vapor deposition technologies were used to deposit two-segment coatings with Cr-CoAl -ON based bottom segment and Mn-CoO top segment. The bottom segment serves as a diffusion barrier and bond segment, while the top segment is meant to increase electrical conductivity and inhibit Cr volatility. Coatings were deposited on ferritic steel and subsequently annealed in air for various time intervals. Surface oxidation was investigated using Rutherford backscattering spectrometry, scanning electron microscopy, and energy-dispersive spectrometry analyses. Cr volatilization was evaluated using a transpiration apparatus and inductively coupled plasma-mass spectrometry analysis of the resultant condensate. Electrical conductivity ͑area specific resistance, ASR͒, was studied as a function of time using the four-point technique. Significant improvement in oxidation resistance, Cr volatility, and ASR were observed in the coated versus uncoated samples. Transport mechanisms for various oxidizing species and coating diffusion barrier properties are discussed.

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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 lm) YSZ via LAFAD and FA-EBPVD. LAFAD was found to be effective in applying thin (*1 lm) dense YSZ films on porous substrates at *400°C. FA-EBPVD produced relatively thick (*10-20 lm) dense YSZ coatings on porous substrates, with columnar morphology and nano-metrical grain size. A *10 lm FA-EBPVD YSZ coating was observed to bridge NiO/YSZ surface pores of *10 lm, 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.