Alumina/zirconia nanopowders, with up to 20 mol% Al2O3, were prepared by wet-chemical synthesis technique, using controlled hydrolysis of alkoxides. The as-synthesized powders are amorphous, have very high specific surface area and the corresponding particle size smaller than 4 nm. Amorphous powders with 0, 10 and 20 mol% Al2O3 crystallize at 460, 692 and 749 degrees C, respectively, as a single-phase tetragonal zirconia, without any traces of alumina phases. Rietvled refinement of X-ray diffraction data, used for the detailed structural analysis of annealed nanopowders, showed that the high-temperature zirconia phase is stabilized due to the formation of ZrO2/Al2O3 solid solutions. High solubility of alumina in the tetragonal zirconia (up to 28.6 at% Al3+) and stabilization of tetragonal zirconia solid solution up to high temperature (as high as 1150 degrees C) were also confirmed. (C) 2007 Elsevier Ltd. All fights reserved.