Abstract: The nonlinear electrical properties of TiO₂·Y₂O₃·Nb₂O₅ ceramics were investigated as a new varistor material. An optimal
doping composition of 99.75%TiO₂·0.60%Y₂O₃·0.10%Nb₂O ₅was obtained with low breakdown electrical field of 8.8V/mm, high nonlinear constant of 7.0 and ultrahigh
relative dielectric constant of 7.6×10⁴, being consistent with the highest and narrowest grain boundary barriers of the ceramic. The frequency dependence of the
capacitance and the resistivity shows that the samples doped with 0.10%mol Nb₂O₅ exhibit the highest capacitance and resistivity at low frequencies and comparatively low in
comparison with other samples at high frequencies. In view of these electrical characteristics; the ceramic of 99.75%TiO₂·0.60%Y₂O₃·0.10%Nb₂O₅ is a viable
candidate for capacitor-varistor functional devices. The characteristics of the ceramics can be explained by the effect and the maximum of the substitution of Ti⁴⁺ with Nb⁵⁺.
In order to illustrate the grain boundary barriers formation in TiO₂·Y₂O₃·Nb₂O₅ varistors, a grain-boundary defect barrier model was also introduced.

Key words: varistors, titania, electrical properties, frequency dependence