Synthesis of a Thin-Layered Ionic Conductor, CeO₂−Y₂O₃, by Atomic Layer Deposition in View of Solid Oxide Fuel Cell Applications

Thin films of yttria-doped ceria (YDC) electrolyte were processed for the first time by atomic layer deposition (ALD) for solid oxide fuel cell (SOFC) applications. The β-diketonate complexes Y(thd) 3 and Ce(thd) 4 were used as yttrium and cerium precursors, respectively, whereas ozone was used as the oxygen source. Four-hundred-nanometer thick YDC films were deposited at 300 °C on soda lime, Si(100), stainless steel (430), La 0.8 Sr 0.2 FeO 3 (LSF) cathodes, and on Ni-YSZ anodes. Thickness, crystallinity, and morphology of YDC films were determined by UV−vis spectroscopy, XRD, and SEM/EDX, respectively. Electrical properties of the thin films in the range of 250−475 °C were characterized by impedance spectroscopy. The deposited layers were crystalline as deposited, without any need for annealing. SEM observations showed that the films were homogeneous and well-covering. Their conductivities were significantly lower than those reported in the literature for bulk YDC. Nevertheless, electrical properties of YDC thin films seem to be superior to those of the YSZ thin films, characterized under the same conditions, in the temperature range of 500−750 °C. Thus, YDC by ALD represents a new and promising SOFC generation.