Supercritical fluid deposition of compositionally uniform yttria stabilized zirconia films
Résumé
We report the formation of yttriastabilizedzirconia (YSZ) thin films by supercriticalfluiddeposition (SFD) in carbon dioxide at 20 MPa and a stage temperature of 300 °C via hydrolysis of zirconium(IV) hexafluoroacetylacetonate and yttrium(III) hexafluoroacetylacetonate. Post-deposition annealing of the films at 800 °C yields crystalline films having the expected fluorite structure as evidenced by X-ray diffraction. Such films are suitable for the fabrication of electrolyte thin films for micro-solid oxide fuel cells (μ-SOFC). We show that a cyclic co-deposition process in which aliquots of precursor are introduced sequentially enables the depostion of YSZ thin films with uniform composition as evidenced by X-ray photoelectron spectroscopy. In each cycle, the mixed precursor solution in CO2 is introduced to the reactor and then purged following a short reaction interval. By contrast, simple batch SFD processes that employ hydrolysis of the mixed precursors introduced at the onset of the depositions lead to non-uniform distributions of the cations throughout the thickness of the films. The cyclic deposition approach extends supercriticalfluiddeposition to materials such as multi-cations oxides for which precise control of stoichiometry is required.