urea as a combustion fuel. The fabrication was carried out by refluxing a mixture of cobalt nitrate and urea followed by calcination, for 3 h in static air atmosphere, at 400 °C. The thermal genesis of the Co3O4 was explored by means of thermogravimetric and differential thermal analyses in air atmosphere in the temperature range 25-1000 °C. X-ray diffraction, Fourier transform infrared spectra, and scanning electron microscopy were used to characterize the structure and morphology of the Co3O4. The obtained results conrmed that the resulting oxides were comprised of pure single-crystalline Co3O4 nanoparticles. Moreover, various comparison experiments showed that several experimental parameters, such as the reflux time and the urea/cobalt nitrate molar ratio, play important roles in the crystallite size as well as the morphological control of Co3O4 powders. Consequently, the minimum crystallite size can be obtained at 12 h reflux and a urea/cobalt nitrate molar ratio of 5.