Preparation, characterization, and giant dielectric permittivity of (Y3+ and Nb5+) co-doped TiO2 ceramics

The microstructure and giant dielectric properties of Y3+ and Nb5+ co-doped TiO2 ceramics prepared via a chemical combustion method are investigated. A main rutile-TiO2 phase and dense ceramic microstructure are obtained in (Y0.5Nb0.5)xTi1-xO2 (x = 0.025 and 0.05) ceramics. Nb dopant ions are homogeneously dispersed in the microstructure, while a second phase of Y2O3 particles is detected. The existence of Y3+, Nb5+, Ti4+ and Ti3+ as well as oxygen vacancies is confirmed by X-ray photoelectron spectroscopy and X-ray absorption near edge structure analysis. The sintered ceramics exhibit very high dielectric permittivity values of 104-105 in the frequency range of 40-106 Hz. A low loss tangent value of ≈0.08 is obtained at 40 Hz. (Y0.5Nb0.5)xTi1-xO2 ceramics can exhibit non-Ohmic behavior. Using impedance spectroscopy analysis, the giant dielectric properties of (Y0.5Nb0.5)xTi1-xO2 ceramics are confirmed to be primarily caused by interfacial polarization.