Zirconia (C-ZrO2 = 3-16 wt%) coated silicas (A-380, OX-50, Si-60) were studied using XRD, XPS, FTIR, nitrogen adsorption-desorption, SEM, and quantum chemistry methods. Structure of grafted zirconia depends on the structural characteristics of the silica matrices. The XRD data show the presence of monoclinic, tetragonal and amorphous ZrO2 phases with contribution and crystallite size dependent on the matrix type. The silica gel (ZrO2 crystallite of 3-8 nm in size) or OX-50 (4-5 nm) matrices inhibit the formation of large zirconia crystallites stronger than nanosilica A-380 (13-32 nm) but more uniform ZrO2 coating is formed at the OX-50 surface. The XPS data reveal the formation of the Si-O-Zr bonds in the ZrO2/SiO2 composites, besides individual zirconia and zirconium hydroxide phases. (c) 2009 Elsevier B.V. All rights reserved.