The Effects of Additive on Microstructure and Electrical Properties of BaTiO3 Ceramics

Abstract

In this paper comparative investigations of microstructure and dielectric properties of BaTiO₃ ceramics doped with 1.0 wt% of Nb₂O₅, MnCO₃ and CaZrO₃ have been done. BaTiO₃ samples were prepared using conventional method of solid state sintering at 13000 ^oC for two hours. Two distinguish microstructural regions can be observed in sample doped with Nb₂O₅. The first one, with a very small grained microstructure and the other one, with a rod like grains. In MnCO₃ and CaZrO₃ doped ceramics the uniform microstructure is formed with average grain size about 0.5-2 µm and 3-5 µm respectively. The highest value of dielectric permittivity at room temperature and the greatest change of permittivity in function of temperature were observed in MnCO₃/BaTiO₃. In all investigated samples dielectric constant after initially large value at low frequency attains a constant value at f ≥ 6 kHz. A dissipation factor is independent of frequency greater than 10 kHz and, depending of systems, lies in the range from 0.035 to 0.25. At temperatures above Curie temperatures, the permittivity of all investigated samples follows a CurieWeiss law. A slight shift of Curie temperature to the lower temperatures, in respect of Curie temperature for undoped BaTiO₃, was observed in all investigated samples.