Search

A series of co-doped TiO2 ceramics named (Re0.5Nb0.5)0.005Ti0.995O2 (Re = La, Nd, Sm, Gd) were prepared by a solid-state reaction method. The microstructure, dielectric properties, and impedance spectra of (Re0.5Nb0.5)0.005Ti0.995O2 ceramics were systematically investigated in detail. The co-doped TiO2 with rutile structure ceramics possessing CP and low dielectric loss (<0.05) have been gotten. Low dielectric loss is attributed to enhancing grain boundary resistance and suppressing Maxwell–Wagner polarization This work maybe give us enlightenment about how to find low dielectric loss in co-doped TiO2 CP ceramics. [ABSTRACT FROM AUTHOR]

Dielectric spectroscopy was carried out for reduced and stoichiometric La0.0025Nb0.0025Ti0.995O2 ceramics synthesized by sintering in different atmospheres. A giant permittivity (~1 × 104) was obtained at a frequency of 100 MHz and temperature range from 170 to 350 K. Three dielectric relaxation mechanisms were observed within the temperature range of 10‐300 K via dielectric spectroscopy. A low temperature dipole relaxation peak (in the temperature range of 10‐30 K) in the spectra was identified to be associated with the giant permittivity specifically measured at 100 MHz. The origin of such giant permittivity was attributed to dipole orientation polarization. Hopping polaron and interfacial effect contributed to giant permittivity. After annealing treatment, all the relaxation contributions were weakened. Low dielectric loss was attributed to high resistance of grain and grain boundaries. Annealing in ambient conditions led to decreased relaxation times which gives the signature of decreased concentration of oxygen vacancies and Ti3+. Dipoles which were related to oxygen vacancies and Ti3+, resulted in giant permittivity up to 100 MHz. [ABSTRACT FROM AUTHOR]

(In0.5Nb0.5)0.005(Ti1‐xZrx)0.995O2 (INZT, x = 0‐0.10) ceramics were synthesized using a conventional sintering method, and the effects of Zr content on the microstructures, dielectric properties and electron‐pinned defect‐dipoles (EPDD) polarization of the resultant products were investigated. The solubility limit of INZT was x = 0.075, and a secondary ZrTiO4 phase appeared at x = 0.10. Ceramics with x = 0‐0.10 exhibited excellent dielectric properties, ie, colossal permittivity (CP, εʹ > 103) and low dielectric loss (tanδ < 0.1), over a wide range of frequencies (100‐106 Hz at 300 K) and temperatures (50‐350 K at 1 kHz). The dielectric spectra and XPS results confirmed that the CP property of the ceramics could be ascribed to their EPDD polarization. The activation energy (Ea) for EPDD polarization was continuously enhanced by increasing x values. EPDD relaxation parameters at different x values were revealed using Cole‐Cole equation fitting. Moreover, α, which characterize the relaxation time τ distribution, increased with x values, thus indicating that Zr was involved in and affected electron localized states. The high Ea, temperature Tp of the peak εʹʹ at 1 kHz, and dielectric relaxation time τp at 30 K were related to increases in hopping distance of electrons among defect clusters with Zr addition. [ABSTRACT FROM AUTHOR]