Dielectric and ferroelectric properties of Zn and Mn doped BaTiO3 : After optimizing the calcination temperature

The present work aims to study the effect of calcination temperature on structure and phase formation of BaTiO3 powder. Barium Titanate (BaTiO3) powder was synthesized by mixing high purity BaCO3 and TiO2 powder using agate mortar in acetone medium for 6 hours. The powder mixture was dried and kept at 60oC. The soft agglomeration was broken and the sample was divided into three portions each weighing 5gm each. These three samples were calcined at 700oC, 800oC and 900o C for 5 h with heating and cooling rates of 10oC/min. Phase transformation and particle size of the calcined powders have been investigated as a function of calcination temperature, by room-temperature X-ray diffraction techniques. It was seen that the perovskite-like phase of BaTiO3 was successfully obtained and this was compared with the standard sample. With increasing calcination temperature, BaTiO3 transformed from the cubic to the tetragonal phase. The X-ray diffraction investigations have revealed that the samples calcined at 9000C perfectly coincide with original spectrum. After finding the optimum calcination temperature, the second aim was to prepare Ba0.95Zn0.05TiO3, BaTi0.95Mn0.05O3 and Ba0.95Zn 0.05Ti0.95Mn0.05O3 under the same conditions and compare with pure BaTiO3. The X-ray diffraction analysis was performed to confirm whether the desired samples were formed. P-E hysteresis loop was analyzed and the hysteresis loop was observed for pure BaTiO3 and BaTiMnO3, due to the formation of oxygen vacancies and exchange interaction-induced polarization. The small area of P-E loop indicates better homogeneity and crystallinity of prepared samples. The dielectric constant of Mn doped sample is increased and Curie temperature is lowered. The samples with Zn dopants are behaving in an entirely different way. They do not exhibit a perfect dielectric behavior but shows a semiconducting property which is confirmed from the band gap measurement.