High-temperature superconductor materials for contact layers in solid oxide fuel cells: II. Chemical properties at operating temperatures Original Research Article

The chemical reactivity between superconducting ceramic materials (YBa2Cu3O7−x, Bi2Sr2CaCu2O8+x and Bi2Sr2CuO6+x) and the cathode material of solid oxide fuel cells (La0.65Sr0.3MnO3) was investigated by long-term annealing experiments of pressed powder mixtures lasting two weeks at 850°C. The chemical properties at the operating temperature of a solid oxide fuel cell revealed that all three superconducting materials reacted with La0.65Sr0.3MnO3 and underwent changes in volume and density after annealing. The chemical compatibility between the superconductors and interconnect material, a ferritic steel (X 10 CrAl 18), was investigated using screen-printed thick layers of Bi2Sr2CuO6+x on steel substrates. The formation of undesirable products, especially SrCrO4, due to diffusion processes across the interface was confirmed by investigations of metallographic cross-sections. Efforts to stop the interfacial reaction by introducing a thin CuO barrier layer between the superconductor and steel did not solve the problem.