Enhanced electrical properties of BaTiO3-based thermosensitive ceramics for multilayer chip thermistors applications by addition of (Bi0.5Na0.5)TiO3

摘要

BaTiO3-based multilayer chip thermistors with the inner electrodes have been designed to meet the requirements of miniaturization and low resistance. Generally, they were prepared by the reduction-reoxidation method to avoid the oxidization of internal electrodes. Due to their limited efficiencies of oxygen adsorption during the process of reoxidation, positive temperature coefficient of resistivity (PTCR) jump of multilayer chip thermistors were difficult to reach a high value. In this work, we have investigated the influence of (Bi0.5Na0.5)TiO3 (BNT) addition and sintering temperature on microstructure and electrical properties of BaTiO3 based multilayer chip thermistor ceramics. The measurement of grain size and density suggested that a moderate addition of BNT could facilitate grain growth when the ceramic is sintered at a suitable temperature. This phenomenon was attributed to the liquid Na-rich phase at a suitable temperature, and it was affected by the Na+-rich grain shell during the sintering process. Meanwhile, Bi3+ was found to increase the adsorption efficiency of oxygen at the grain boundaries, thus promoted PTCR jump. Multilayer chip thermistors ceramics with high PTCR jump of 3.55 x 10(3) and low RT resistivity of 18.4 Omega cm were obtained after sintering at 1125 degrees C with 0.3mol% BNT additive.