Dielectric properties of TiO2 co-doped with yttrium and niobium

Abstract

The effects of small contents (up to10 mol%) of Y2O3 and Nb2O5 on the microstructure and dielectric properties of TiO2 were investigated, aiming to identify the underlying mechanism in the colossal permittivity of co-doped specimens. Sintered materials were prepared by the solid state reaction method and characterized by X-ray diffraction, scanning electron microscopy, and electrochemical impedance spectroscopy. All sintered specimens exhibited the characteristic tetragonal TiO2 rutile phase. Secondary phases were detected at the grain boundaries, independent on the sintering temperature. The mean grain increased with both sintering temperature and co-dopants content. The higher electric permittivity was obtained for specimens with 5 mol% of co-dopants, sintered at 1480ºC, and the lowest value of the dissipation factor for samples with 10 mol%, sintered at 1500ºC. The dielectric properties of co-doped TiO2 were attributed to the internal barrier layer capacitance and electron-pinned dipole defect mechanisms.