Indium (111) and tin (IV) hydroxides (precursor) were synthesized by a co-precipitation process at the different reaction temperature in a water bath. Nanocrystalline indium tin oxide (ITO) powders with spherical and rod shapes were obtained upon calcination. The phase transformations during calcination process in Ar gas at ambient temperature -1100 degrees C were investigated by TG/DTA system, X-ray diffraction and transmission electron microscopy. A mixture of In(OH)(3), InOOH and Sn3O2(OH)(2) preferred the path of pure In(OH)(3) -> In2O3 during calcinations in Ar gas and the powders with rhombohedral and cubic structured crystalline ITO were obtained at 600 degrees C. The crystal parameters changed with calcination temperature. Oxygen vacancies were developed at about 400 degrees C determined by resistivity decrease and the color change of powders. Characterized by TEM and FESEM, the spherical and rod shapes of the particles were prepared at bath temperature of 40 and 100 degrees C, respectively, and remained after calcination in Ar gas. The particles' size showed obvious shrinkage compared with the precursors. At higher bath temperature In(OH)(3) octahedral nuclei in the cubic structure cell stacks along the closest plane (100) and evolves nano-rod due to the influence of NH4+ on the orientation of crystals. (c) 2005 Elsevier B.V. All rights reserved.