Zirconia powder with an average particle size of 10 run was prepared by adding carbon nanotubes (CNTs) in the hydrolytic process of ZrO(NO3)(2). The formation of zirconia nanoparticles was attributed to the addition of CNTs, which affected the zirconia precursor structure. The relation between the stability of cubic (c) and tetragonal (t) phase zirconia at room temperature, and the zirconia particle size and addition of carbon was studied. It was revealed that zirconia particles with nanometer size had took the form of t-phase and that the addition of carbon tended to favor m-phase ZrO2 to c-phase ZrO2 transformation and c-phase ZrO2 stabilization at low temperature. (C) 2004 Elsevier B.V. All rights reserved.