This could be attributed to a recrystallization mechanism during solid state sintering and also a deviation from stoichiometric compositions derived from mixed oxide route.After mixing with NiO nano-particles, it was clearly seen that the average grain size significantly reduces to 0.90 μm and continuously decreases with increasing NiO content as depicted shown in Fig. 4. Previous studies [11-12] reported that NiO was identified in the grain boundary areas of the micro-structure, which might act as like a grain growth inhibitor. Therefore, these NiO existing in the regions of grain boundary area might be the origin for the fine grain size in NiO-doped BTO ceramic.micrographs�