Nonlinear electrical behavior and dielectric properties of (Ca, Ta)-doped TiO 2 ceramics

Abstract

TiO 2 ceramics doped with 2.5 mol% Ta and different concentrations of Ca were obtained by sintering at 1300°C. As a varistor material, the nonlinear electrical behavior and dielectric properties of these ceramics were investigated. The ceramics have nonlinear coefficients a in the range 2.0–5.5 and high relative dielectric constants. The effects of Ca on the density, nonlinear electrical behavior, resistivity and dielectric properties of the Ta-doped TiO 2 ceramics were also studied. The sample doped with 0.75 mol% Ca and 2.5 mol% Ta exhibits the highest nonlinear coefficient and a comparatively lower relative dielectric constant. By analogy to a grain-boundary defect model, the nonlinear electrical behavior of the TiO 2 system is explained.