Transition metal oxides with perovskite structure (such as niobium, tantalum-based semiconductor materials) have attracted considerable attention in recent decades due to their interesting properties and potential applications [1]. NaTaO3 materials have been identified as potential high-performance thermoelectric materials, by offering an important thermoelectric-performance advantage for generating electrical energy from heat sources. Undoped NaTaO3 were successfully synthesized by sol-gel method, using tantalum ethoxide and sodium hydroxide, and as chelating agent citric acid was used. The as obtained materials were heat treated for 6 hours at different temperatures (600, 800, respectively 1000 °C), the heating rate in all the cases was 5°C/min. The obtained powders were characterized by X-ray diffraction (XRD) using PANalytical X‟PertPRO MPD Diffractometer. Powder morphology was observed using an Inspect S PANalytical model scanning electron microscopy (SEM). The semiquantitative elemental analysis was analyzed through EDX facility of SEM. Figure 1.(a) shows XRD patterns for the samples prepared at different calcinations temperatures for 6 h. From X-ray diffraction (XRD) analysis it can be observed high degree of crystallinity of undoped NaTaO3 calcined at 800 °C. Clearly, the temperature exerts a great influence on the formation of NaTaO3 materials. a) b) c) Figure 1. XRD patterns of undoped NaTaO3 at different thermal treatment (a); SEM image (b) and EDX spectrum (c) of NaTaO3 calcined at 800 °C The morphology of the NaTaO3 samples synthesized by sol-gel method and annealed at 800 °C was studied by scanning electron microscopy (SEM) as shown in Figure 1 (b). The SEM analysis shows that the particles have the same shape and is strongly agglomerated. From the analysis of the solid composition (Figure 1(c)) we can see that the as-prepared powder consist of pure NaTaO3.