Intercalation of Thin-Film Gd-Doped Ceria Barrier Layers in Electrolyte-Supported Solid Oxide Cells: Physicochemical Aspects

To minimize alteration of the La0.6Sr0.4Co0.2Fe0.8O3-delta(LSCF)/Gd0.2Ce0.8O2-delta(CGO20)/Y0.06Zr0.94O2-delta(3YSZ) interface via strontium zirconate formation in solid oxide cells, electron beam physical vapor deposition was employed to manufacture dense, thin gadolinium-doped ceria (CGO) interlayers. CGO layers with thicknesses of 0.15, 0.3, and 0.5 mu m were integrated in state-of-the-art 5 x 5 cm(2)-large electrolyte-supported cells, and their performance characteristics and degradation behavior were investigated. Electrochemical impedance spectroscopy measurements are correlated with a postmortem scanning electron microscopy/energy-dispersive X-ray spectroscopy analysis to show that 0.15 mu m thick layers lead to the formation of a continuous Sr-containing secondary phase at the CGO/YSZ interface, likely related to the formation of a SrO-ZrO2 phase. Major performance losses were confirmed by an increase in both Ohmic and polarization resistance with an increase in the frequency region similar to 10(3) Hz. Cells with 0.3 mu m- and 0.5 mu m-thick CGO layers showed similar high performance and low degradation rates over a testing period of similar to 800 h. The YSZ/CGO interface of the cells with a 0.3 mu m-thick CGO layer showed the formation of a discontinuous Sr-containing secondary phase; however, performance losses were still successfully prevented. Furthermore, it is observed that 0.5 mu m-thick CGO layers were sufficient to suppress the formation of the Sr-containing secondary phase.