Thin-film proton BaZr0.85Y0.15O3 conducting electrolytes:: Toward an intermediate-temperature solid oxide fuel cell alternative

A novel method for the preparation of a thin oxidic proton-conducting electrolyte is presented. This kind of supported film was studied in detail as it is applicable for IT-SOFC, H-2 membranes, and advanced catalytic converters. Thin-film (similar to 5 mu m) proton-conducting membranes with the nominal composition BaZr0.85Y0.15O3-delta (BZY) were prepared over porous Ni-8YSZ/Ni-BZY substrates by the solid-state reaction of a gastight 8YSZ layer and a coated BaCO3 layer. The resulting asymmetric membranes are of a homogeneous composition and are gastight. Indeed, XRD analysis showed a highly crystalline cubic perovskite. The solid-state reaction promoted the formation of (i) an electrolyte with very fine (similar to 100 nm) grains and high packing density and (ii) an unexpected porous needle-like top layer with a nominal composition similar to that of the protonic electrolyte, to which it is intimately attached. The layer morphology, phase distribution, and lattice composition were investigated by EDS-SEM, EDX as well as SIMS. Conduction properties of the protonic material were investigated by DC conductivity of pressed bars under different gas compositions and also by impedance spectroscopy of a supported thin film.