Impedance analysis of Nb2O5 doped BaTiO3-Na0.5Bi0.5TiO3 ceramics

摘要

BaTiO3-based MLCC materials were limited for high temperature applications (temperature range up to 200°C), due to their low Curie temperatures. The addition of Na0.5Bi0.5TiO3(NBT) component in BaTiO3(BT) based ceramics was found to increase the Curie temperature, without sacrificing the dielectric constant. The Curie temperature was reported to increase from 125°C to 156°C with addition up to 10mol%, making it possible to satisfy the X8R or X9R criterions. In addition, the small amount of Nb2O5 dopant in the system leads to a diffused dielectric maxima and improved temperature stability. The NBT-BT with 2wt% Nb2O5 addition was found to exhibit a core-shell structure, while maintaining the dielectric constant at about 2500. To analyze the electrical microstructure variation, the obtained impedance data was fitted by a 4RC equivalent circuit, corresponding to the core, shell, grain boundary, and ceramic/electrode interface regions. All the electrical properties, including the capacitance, activation energy, and conductivity could be well explained by using this equivalent circuit.