Element interdiffusion at electrolyte–cathode interfaces in ceramic high-temperature fuel cells

Ceramic high-temperature fuels cells (or solid-oxide fuel cells, SOFCs) directly convert hydrogen and also hydrocarbons into electrical energy. Recently developed functional materials to be used as cathodes show excellent performance, but they suffer from interfacial reactions with adjacent layers. These reactions lead to a rapid degradation of the fuel cells which limits their potential for application. Therefore, these reactions must be prevented by protective interlayer coatings, for instance by a ceramic (Ce,Gd)O2-δ (CGO) diffusion barrier. This paper discusses selected cathode–interlayer–electrolyte interdiffusion phenomena analysed by transmission electron microscopy (TEM). Different techniques for the application of the CGO diffusion barrier screen-printing and subsequent sintering, and physical vapour deposition–were employed to probe the influence of the processing on the diffusion of chemical species from the functional layers. Moreover, some model experiments were carried out to evaluate the significance of element diffusion on the power density.