Nanostructured ZrO2 coatings are prepared on both dense and porous substrates by wet-chemical deposition of non-agglomerated 5 run precursor particle dispersions, followed by thermal processing. The precursor particle dispersions are made by modified emulsion precipitation and a purification treatment to remove reaction products and additives. The coatings are formed by depositing the precursor nanoparticle dispersion directly onto the substrate, followed by drying and heating at 600 degrees C. Scanning electron microscopy and cross-sectional transmission electron microscopy observations of the heat-treated coatings indicate that the ZrO2 coating on dense Si wafer substrate has a homogeneous, dense particle packing structure with shallow meniscus-shaped depressions in the surface, and microcracks below the meniscus surface. On the other hand, coatings formed on a meso-porous gamma-alumma membrane substrate are free of defects, but with a lower packing density. The mechanism of the substrate effect on the particle packing behavior and defect formation during coating deposition is discussed. It is expected that by using a thin porous substrate with reduced capillary force, a defect-free, homogenously dense-packed coating structure can be achieved. (c) 2007 Elsevier B.V. All rights reserved.