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.
Lithium fluoride (LiF) was selected as a liquid phase sintering additive to lower the sintering temperature. The effects of LiF on the sinterability, microstructure, and electrochemical properties of Ba(Zr 0.8 − x Ce x Y 0.2 )O 3 − δ (0≤ x ≤ 0.4) (BZCYs) ceramics were investigated. Using LiF as an additive, high density BZCYs ceramics can be obtained at sintering temperatures 200-300°C lower than the usual 1700°C with much shorter soaking time.Nuclear reaction investigations showed no lithium and a small amount of fluorine reside in the sample which indicates the non-concomitant evaporation of lithium and fluorine during the sintering process. Scanning electron microscopic investigations showed the bimodal structure of BZCYs ceramics and grain growth as Ce content increases. In a water saturated hydrogen containing atmosphere, BZCYs ceramics have higher conductivity when LiF is used in the sintering process. LiF-added BZCYs electrolyte-supported fuel cells with platinum electrodes were tested at temperatures from 500 to 850°C. Results show that LiF is an excellent sintering additive for lowering the sintering temperature of BZCYs.
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