Thin BaCe0.8Gd0.2O3-δ protonic electrolytes on porous Ce0.8Gd0.2O1.9-Ni substrates

Thin proton-conducting electrolytes with 20 mu m thickness and a nominal composition BaCe0.8Gd0.2O3-delta were prepared over porous substrates composed of Ce0.8Gd0.2O1.9 (CGO)-Ni. The fabrication method includes the simultaneous cofiring and solid-state reaction at 1300 degrees C of three screen-printed layers: mixed conducting anode layer, CGO, and an upper-coated BaCO3 layer. The resulting asymmetric membranes with 5 X 5 cm(2) geometry are gastight. The solid-state reaction resulted in the formation of (i) an electrolyte with large (similar to 2-5 mu m) grains and high packing density and (ii) anode layer comprising finely grained BaCe0.8Gd0.2O3-delta and Ni particles with a thickness around 5 mu m. The layer morphology, phase distribution, and lattice composition has been investigated by X-ray diffraction, energy-dispersive spectroscopy scanning electron microscopy, and secondary-ion mass spectrometry. The preparation of the substrate by warm-pressing and tailoring of the porosity and sintering activity are also thoroughly described. DC-electrical conductivity and ac-electrochemical characterization showed that the supported Gd-doped barium cerate electrolyte produced by solid-state reaction has interesting proton-conduction properties for application in solid oxide fuel cells, hydrogen separation, and sensors. (c) 2007 The Electrochemical Society.