Nanostructured YSZ thin films for solid oxide fuel cells deposited by ultrasonic spray pyrolysis

Nanostructured thin films of yttria-stabilized zirconia (YSZ) have been prepared on single-crystalline silicon substrates by ultrasonic spray pyrolysis using zirconium acetylacetonate and yttrium acetylacetonate hydrate as metallo-organic precursors dissolved in anhydrous methanol. The morphology, structure and electrical properties were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) and impedance spectroscopy (IS). The substrate temperature was optimized for obtaining smooth, dense and homogeneous nanocrystalline films with grains sizes as small as 10 nm. The influence of thermal annealing on structural properties of films was studied. The activation energy measured for electrical conduction through the grains (1.14 eV) was similar to that obtained in bulk of YSZ, but for conduction through the grain boundaries it acquires a value of 0.79 eV, increasing the total conductivity of the material up to 0.033 S/cm at 650 °C. These activation energy values are related to the small grain size and the close boundaries obtained at the optimized conditions. The obtained films are good candidates for applications as electrolytes in solid oxide fuel cells (SOFC) operating at relatively low temperatures.