Perovskite based protective coatings for solid oxide fuel cell metallic inhterconnects

Recent improvements in solid oxide fuel cell (SOFC) performance through the use of anode supported (thin electrolyte) cells has allowed the typical operating temperature to be lowered to 800°C or less. At this operating temperature, lower cost Ni or Fe based metallic interconnects become a potential replacement for the brittle and expensive chromite based ceramic interconnects that were used at higher cell operating temperatures. However, the use of metallic interconnects is not without problems. Typically, the alloys that are under consideration contain Cr at levels such that Cr 2 O 3 is the native oxide grown at elevated temperatures. On one hand, this is preferable since Cr 2 O 3 has a higher electronic conductivity than alternative protective scales, such as SiO 2 and Al 2 O 3 . On the other hand, in the cathode environment Cr 2 O 3 can form a number of vapor species that contribute to cell degradation by contamination of the cathode/electrolyte interface. The coating of chromium containing alloys with LaCrO 3 based perovskites is a potential method of decreasing the contamination effects of Cr vapor species. In this study, magnetron sputtering was used to deposit LaCrO 3 and Ca doped LaCrO 3 thin films. The coated samples were heated in air at various temperatures, and the changes in the film properties as a result of annealing are reported. In addition, annealing in a reducing environment (5% H 2 in N 2 ) was also studied as a method of controlling the reaction pathway for crystallization of the as deposited films. Both the substrates and LaCrO 3 films were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and atomic force microscopy. Area specific resistance (ASR) measurements were also made on the coated samples after the initial annealing step and after 100 hours at 800°C in air.