Effect of Sintering Time on Dielectric Properties of Barium Titanate and Nb Doped Barium Titanate

摘要

Barium titanate (BaTiO_3) with its perovskite structure is a promising dielectric material for many applications such as transducers, actuators, high-k dielectrics and multilayer ceramic capacitors (MLCC). In this study, we have investigated the effect of sintering time on dielectric properties of BaTiO_3 and Nb-doped BaTiO_3. BaTiO_3 was doped with 0.3 mol% niobium oxide (Nb_2O_5). At first, nano sized pure BaTiO_3 and Nb_2O_5 doped BaTiO_3 were milled, dried and pressed into pellets to prepare green samples. Then, the samples were sintered at 1275°C for different time periods ranging from 2 to 5 hrs. Single stage sintering was adopted for the densification of prepared samples. Microstructure of the sintered samples was investigated employing Field-emission scanning electron microscope (FESEM). Dielectric properties of the samples were measured using an impedance analyzer. Finally, a correlation was established between the dielectric properties of the sintered samples and their microstructure. Nb has shown to provide strong inhibiting effect after sintering the samples in the range of 2 to 5 hours at 1275°C thereby, resulted in higher dielectric properties of doped BaTiO_3 ceramics compared to that of pure BaTiO_3. The best room temperature dielectric constant of 7200 was obtained for Nb doped BaTiO_3 sintered at 1275°C for five hours. Such improved dielectric constant is attributed to the optimum grain size of about 1 micron at this sintering temperature.