Nonlinear Electrical Behaviour of the TiO ₂ ·Y ₂ O ₃ ·Nb ₂ O ₅ System

Abstract

The nonlinear and 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 6-12 V·mm-1, in which the varistor of (99.3 mol%)TiO2·(0.6 mol%)Y2O3·(0.1 mol%)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 85 000, 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 varistor has varistor-capacitance bifunctional components, which are quite useful in the situation that the voltage protection and high-frequency noise absorption are meanwhile required.