Can we achieve significantly higher ionic conductivity in nanostructured zirconia?

Works on nanostructured ZrO2, including nanocrystalline ceramics, polycrystalline and epitaxial thin films, and heterostructures, are evaluated. Lower total conductivity has been achieved for nanocrystalline ceramics and polycrystalline thin films. Higher conductivity was reported for epitaxial films, but this might be an artefact of the substrate. The colossal ionic conductivity that was claimed for heterostructures has now been demonstrated to be electronic in origin. However, distinctively different properties may appear in ZrO2 for grain sizes <5 nm.