Colossal dielectric permittivity in co-doping SrTiO3 ceramics by Nb and Mg

(Mg + Nb) co-doped SrTiO3 dielectric ceramics were prepared using a solid-phase synthesis method to investigate dielectric properties as a function of doping contents, temperature, and frequency. A very low dielectric loss (0.0354, at 1 kHz) and colossal permittivity (21026, at 1 kHz) were observed in Sr(Mg1/3Nb2/3)(x)Ti1-xO3 (x = 5%) at room temperature. The dielectric properties showed good frequency stability while three significant dielectric relaxations appear over a wide temperature range: -155 degrees C-500 degrees C. Combining with the X-ray photoelectron spectroscopy results, the mechanism of the colossal permittivity in our samples was discussed according to electron-pinned defect-dipoles model.