Nonlinear Electrical Behaviour of the TiO₂.Y₂O₃.Nb₂O₅ System

The nonlinear properties and the dielectric properties of a new TiO₂-based varistor system, TiO₂.Y₂O₃.Nb₂O₅, have been investigated. The (Nb, Y)-doped TiO₂ ceramics have nonlinear coefficients of α =5-8 and a lower breakdown electrical field of 6-12V.mm^-1, in which the varistor of (99.3mol%)TiO₂.(0.6mol%)Y₂O₃.(0.1mol%)Nb₂O₅ composite sintered at 1400°C has a nonlinear coefficient of α =7.8 and a maximum breakdown electrical field of 12 V.mm^-1 at 1 mA.cm^-2. Also, the relative dielectric constants of the composite reach more than 85000, which is almost unchanged within the temperature range from -20 to 280°C and the frequency range of 0.5 K-2 MHz. Due to these properties the (Nb, Y)-doped TiO₂ varistors has varistor capacitance bifunctional components, which are quite useful in the situation that the voltage protection and high frequency noise absorption are meanwhile required.