An extensive work for the study of SnO2 samples doped with x-mol% of Sb (x = 0, 6, 10, 14 and 18) is reported. The materials were prepared by the polymeric precursor method (Pechini method), calcined for 4 h between 800 8C and 1200 8C. The Rietveld method with X-ray diffraction data (XRD) was used to analyze the unit cell dimensions, crystallite size and microstrain. It was observed the crystallite size increasing and decrease of the microstrain with the increase of the calcining temperature. The synthesis of tin oxide nanoparticles with high thermal stability against particle growth rate was achieved by doping SnO2 particles with Sb2O3. All the phases tend to have the same dimension when the temperature increases, although its values varies with x and reaches the maximum value when fired at 1100 8C. These variations seem to be an indication that the oxidation state of the antimony changes with the amount of Sb added to the material