Colossal permittivity of (Li, Nb) co-doped TiO ₂ ceramics

In this work, (Li, Nb) co-doped TiO ₂ ceramics (LNTO _x , x < 0.1), were synthesized through a conventional solid state reaction method. As revealed by X-ray diffraction (XRD) spectra, all LNTO ceramics exhibited pure tetragonal rutile structure. The LNTO _0.01 ceramic showed a colossal permittivity over 7000 and a low dielectric loss (tgδ < 0.06) in a wide frequency range of 10 ² Hz–10 ⁷ Hz. The dielectric spectra under DC biases were tested at different temperatures. The experimental data could fit the modified Debye equation well. It was found that there are multiple dielectric polarization mechanisms in LNTO ceramics including space charge polarization, relaxor-type relaxation, polaron hopping and dipole polarization related with localized electrons.