Study On The Preparation And Properties Of TiO₂ Capacitor-varistor Double Functional Ceramics

With the highly nonlinear electrical characteristics, varistors are widely used as the surge protection in relatively low voltage circuits, lightning arresters and the transient protection in electronic power systems. The study on new varistor materials whose main component is TiO2 is at the moment of deep development and several problems are to be solved. Because of these problems, TiO2 based varisors were comprehensively analyzed in this paper.Two different series of samples was prepared by the way of doping. The effect of component of doping on varistor material was investigated. Some theories and models was analysed in the base of experiment. The main working and results are as follows:(1) The influence of some technology processes to the varistor ceramics has been discussed.(2) The effect of Bi2O3 doping (0.05-1.0mol%) on the nonlinear electrical behavior and dielectric properties of TiO2·Nb2O5-based ceramics has been investigated. The results show that the sample containing 0.2mol% Bi2O3 has the highest nonlinear coefficientαof 6.615 . As the increase of the amount of Bi2O3, the dielectric constant(measured at 1kHz)of samples first drop and then increase.The sample containing 0.2mol% Bi2O3 has the lowest dielectric constant.(3) The electrical properties of TiO2 ceramics with various Sb2O3 contents have been investigated. The results show that the sample containing 0.2 mol% Sb2O3 has the highest nonlinear coefficientαof 13.23. According to these characteristics, the Sb2O3·TiO2 ceramics are viable candidates for capacitor-varistor functional devices. In order to illustrate the grain boundary barrier formation in Sb2O3·TiO2 varistors, an interface defect model was introduced.