Nonlinear electrical properties of TiO2•Y2O3•Nb2O5 capacitor-varistor ceramics

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%Nb2O5 was obtained with low breakdown electrical field of 8.8V/mm, high nonlinear constant of 7.0 and ultrahigh relative dielectric constant of 7.6 X 10(4), 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 gain-boundary defect barrier model was also introduced.