Colossal permittivity in (In 1/2 Nb 1/2 ) x Ti 1−x O 2 ceramics prepared by a glycine nitrate process

(In + Nb) co-doped TiO2 nanoparticles with very low dopant concentrations were prepared using a glycine nitrate process. A pure rutile—TiO2 phase with a dense microstructure and homogeneous dispersion of dopants was achieved. By doping TiO2 with 1.5% (In + Nb) ions, a very high dielectric permittivity of ε′ = 42,376 and low loss tangents of tanδ = 0.06 (at room temperature) were achieved. The large conduction activation energy at the grain boundary decreased with decreasing dopant concentration. The colossal permittivity was primarily attributed to the internal barrier layer capacitor (IBLC) effect. The dominant effect of interfacial polarization at the non–Ohmic sample–electrode contact was observed when the dopant concentration was ≤1.0 mol%. Interestingly, the sample–electrode contact and resistive–outer surface layer effects, i.e., surface barrier layer capacitor (SBLC) effect, has also an effect on the colossal dielectric response in (In + Nb) co-doped TiO2 ceramics.