Preparation and properties of TiO2 varistors

Abstract

TiO2 varistors with low resistivity were developed to operate at low voltages and have a reasonably high nonlinearity index. The varistor properties of TiO2 ceramics are due to two different groups of dopants. Pentavalent cation dopants are used to decrease the TiO2 lattice resistivity to ≃10–100 Ω cm at 25°C. Divalent cation dopants with large ionic radii are introduced to the grain boundary region by segregation process during cooling to provide a localized transport barrier. Thus, the conductive grain lattice and the resistive grain boundaries result in a low voltage varistor.