Barium titanate nano-sized powders had been prepared by a slightly modified Pechini method. DTA/TG thermal analysis indicated that thermal decomposition of the precursor proceeds through four major step processes: (a) dehydration reaction, (b) combustion reactions, (c) intermediate phases formation, and (d) decarbonation of the intermediate to give BaTiO 3 . X-ray diffractometry (XRD) and Raman spectroscopy results indicated that, depending on the heating-rate, the BaTiO 3 formation took place via a predominant solid-state reaction between nano-sized BaCO 3 and amorphous TiO 2 (TiO 2−x ) when crystallized by low heating-rate (1.5°C min −1 ). Although a small amount of a quasi-amorphous intermediate phase was also present. BaTiO 3 crystallization by rapid heating-rate (5°C min −1 ) took place through a quasi-amorphous intermediate phase formation as the main rate-controlling factor for the crystallization process. Although room temperature XRD results seems to indicate the formation of pseudo-cubic BaTiO 3 as the final reaction product, the Raman spectra indicated as more probable the formation of a mixture of an oxygen-deficient hexagonal and tetragonal BaTiO 3 phases below 700°C. Above that temperature, the tetragonal BaTiO 3 was the only phase present.