Nonlinear electrical properties of MnO2-doped TiO2 capacitor varistor ceramics

MnO2-doped TiO2 varistors were prepared by the conventional solid state reaction. The effects of a small amount of MnO2 (0–0.6 mol%) on the microstructure and electrical properties of TiO2 varistor samples were investigated. X-ray diffraction patterns indicate that a single phase of TiO2 rutile structure without any secondary phases is obtained in all samples. The microstructure of TiO2 varistors becomes more homogeneous when doped with 0.3 mol% MnO2 and these samples exhibit excellent electrical properties, in which the breakdown voltage is 4.95 V/mm, the dielectric constant is 11.09 × 104, the nonlinear coefficient is 5.07 and the tan δ is 0.1618. The excellent electrical properties should be ascribed to the synergetic effect of the homogeneous microstructure, adequate oxygen vacancies and the formation of an effective grain boundary barrier induced by MnO2 doping.