Nonlinear I-V behavior in colossal permittivity ceramic:(Nb+In)co-doped rutile TiO₂

The new (Nb+In) co-doped TiO₂ ceramics recently stimulated considerable attention due to their colossal permittivity (CP) (~100,000). In this research, the 3 mol% (Nb+In) co-doped TiO₂ ceramics were synthesized by an standard solid-state reaction method. Phase structure was studied by XRD and Raman, which showed that all samples were in pure rutile phase. The elements distribution was tested by the SEM-EDS, indicating that the Nb and In ions were homogeneously distributed in the grain and grain boundary. Dielectric properties and I-V behavior analysis demonstrated that the ceramics may compose of semiconducting grains and insulating grain boundaries. The existence of CP and nonlinear I-V behavior in sample had been explained by an internal barrier layer capacitance (IBLC) model, which consists of n-type semiconductor grains and insulating grain boundaries.