Cubic ZrO2 nanocrystals were successfully synthesized through a novel reduction-oxidation route, in which metal zirconium was reduced from zirconium tetrachloride (ZrCl4) by sodium, and then oxidized in atmosphere. The crystals were characterized by high temperature X-ray powder diffraction and transmission electron microscopy. It was shown that cubic nanocrystalline ZrO2 with high crystallinity was obtained, which consists dominantly of spherical particles with an average size of 17 nm or so. (C) 2003 Elsevier B.V. All rights reserved.