Defect Complex Effect in Nb Doped TiO Ceramics with Colossal Permittivity

Donor-doped NbTiO (x = 1%, 2%, 4%, 6%, and 8%) ceramics with giant permittivity (>10) and a very low dielectric loss (∼0.05) were sintered under flowing N at 1400°C for 10 h. By increasing Nb doping concentration, two different dielectric responses were evidenced in the frequency dependence of dielectric properties of Nb doped TiO ceramics, which corresponded to the space charge polarization and the electron-pinned defect-dipoles effect, respectively. Especially, combined with the x-ray photoelectron spectroscopy results, the electron-pinned defect-dipoles induced by the 2(Nb5+)Ti∙→4(Ti3+)Ti′←Vo∙∙ defect complex were further confirmed to give rise to both their high ε and low tan δ in the high frequency range for the NbTiO ceramics with x > 4%.