Surface barrier layer effect in (In + Nb) co‐doped TiO2 ceramics: An alternative route to design low dielectric loss

Abstract Giant dielectric permittivity (ε′) with low loss tangent (tanδ) was reported in (In + Nb) co‐doped TiO 2 ceramics. Either of electron‐pinned defect‐dipole or internal barrier layer capacitor model was proposed to be the origin of this high dielectric performance. Here, we proposed an effectively alternative route for designing low‐tanδ in co‐doped TiO 2 ceramics by creating a resistive outer surface layer. A pure rutile‐TiO 2 phase with a dense microstructure and homogeneous dispersion of dopants was achieved in (In + Nb) co‐doped TiO 2 ceramics prepared by a simple sol‐gel method. Two giant dielectric responses were observed in low‐ and high‐frequency ranges, corresponding to extremely high ε′≈10 6 ‐10 7 and large ε′≈10 4 ‐10 5 , respectively. After annealing in air, a low‐frequency dielectric response disappeared and could be restored by removing the outer surface of the annealed sample, indicating the dominant electrode effect in the initial sample. Annealing can cause improved dielectric properties with a temperature‐ and frequency‐independent ε′ value of ≈1.9 × 10 4 and cause a decrease in tanδ from 0.1 to 0.035. High dielectric performance in (In 0.5 Nb 0.5 ) x T i 1− x O 2 ceramics can be achieved by eliminating the electrode effect and forming a resistive outer surface layer.