Colossal permittivity and impedance analysis of tantalum and samarium co-doped TiO2 ceramics

In this study, (Ta0.5Sm0.5)xTi1−xO2 (x = 0, 0.02, 0.06, 0.15) ceramics (referred to as TSTO) were fabricated by a standard solid-state reaction. As revealed by the X-ray diffraction (XRD) spectra, the TSTOs exhibit a tetragonal rutile TiO2 structure. All the TSTO ceramics display colossal permittivity (~ 102-105). Moreover, the optimal ceramic, (Ta0.5Sm0.5)0.02Ti0.98O2, exhibits high performance over a wide temperature range from 20 °C to 160 °C. At 1 kHz, the dielectric constant and dielectric loss are 2.30 × 104 and 0.11 at 20 °C; they are 3.85 × 104 and 0.64 at 160 °C. Dielectric and impedance spectra analyses for the TSTO ceramics indicate that the CP behavior over a broad temperature range in (Ta+Sm) co-doped TiO2 could be explained by the internal barrier layer capacitance (IBLC) model, which consists of semiconducting grains and insulating grain boundaries.