Ceramic high-temperature fuel cells (or solid oxide fuel cells) are nowadays operated at around 800 degrees C to directly convert hydrogen as well as hydrocarbons into electrical energy. Their outstanding advantage is the high efficiency of this conversion process compared to conventional power generation. Recently developed functional layers to be used as electrodes show excellent performance, however 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 and therefore must be prevented by protective coatings. This paper discusses the performance of solid oxide fuel cells including ceramic (Ce,Gd)O2-delta (CGO) diffusion barrier coatings, which inhibit undesired interfacial reactions between cathode and electrolyte materials. The coatings were applied by different conventional processes like screen printing as well as physical vapor deposition (sputtering, electron beam evaporation). With physical-vapor-deposited CGO thin films the strontium diffusion from the cathode to the electrolyte and the detrimental reaction between the CGO layer and the electrolyte could be avoided, resulting in a significant improvement of the power density of solid oxide fuel cells. (c) 2006 Elsevier B.V. All rights reserved.