Zr0.85Ce0.15O2 nanopowders synthesised by gel-combustion and spray-pyrolysis methods were comparatively studied by means of X-ray diffraction, Raman spectroscopy, thermogravimetric and differential thermal analyses, specific surface area measurements, scanning and transmission electron microscopies and chemical analysis. Fully tetragonal powders were obtained by both methods, as determined by X-ray diffraction and Raman spectroscopy. Both materials exhibited extremely small crystallite sizes (about 6 nm) and high specific surface areas (93 m(2)/g and 42 m(2)/g for gel-combustion and spray-pyrolysis powders, respectively). In both cases, no tetragonal-to-monoclinic transition was observed in the whole temperature range up to 1300 degrees C by differential thermal analysis. The amounts of the expected impurities (Si, B, C) were acceptable and comparable in both cases. (C) 2005 Elsevier Ltd. All rights reserved.