Ionic conduction in zirconia films of nanometer thickness

Polycrystalline 8 mol% Y2O3-stabilized ZrO2 films with thicknesses of 12 and 25 nm were deposited on (1 0 0) MgO substrates, their nanostructures were investigated by means of transmission electron microscopy (TEM), high-resolution TEM and atomic force microscopy, and the electrical properties of the nanostructured films were characterized in dry and humid O2. Compared with microcrystalline bulk ceramics, the ionic conductivity of the nanostructured films is lower by about a factor of 4, which is mainly due to the lower bulk conductivity and the low grain-boundary conductivity. There is not remarkable proton conduction in the nanostructured films when annealed in water vapor, and the influence of the ZrO2/MgO interface on its ionic conduction is negligible.