Colossal Permittivity Characteristics of (Nb, Si) Co-Doped TiO(2) Ceramics

(Nb(5+), Si(4+)) co-doped TiO(2) (NSTO) ceramics with the compositions (Nb(0.5)Si(0.5))(x)Ti(1−x)O(2), x = 0, 0.025, 0.050 and 0.1 were prepared with a solid-state reaction technique. X-ray diffraction (XRD) patterns and Raman spectra confirmed that the tetragonal rutile is the main phase in all the ceramics. Additionally, XRD revealed the presence of a secondary phase of SiO(2) in the co-doped ceramics. Impedance spectroscopy analysis showed two contributions, which correspond to the responses of grain and grain-boundary. All the (Nb, Si) co-doped TiO(2) showed improved dielectric performance in the high frequency range (>10(3) Hz). The sample (Nb(0.5)Si(0.5))(0.025)Ti(0.975)O(2) showed the best dielectric performance in terms of higher relative permittivity (5.5 × 10(4)) and lower dielectric loss (0.18), at 10 kHz and 300 K, compared to pure TiO(2) (1.1 × 10(3), 0.34). The colossal permittivity of NSTO ceramics is attributed to an internal barrier layer capacitance (IBLC) effect, formed by insulating grain-boundaries and semiconductor grains in the ceramics.