Influence of the electric field and annealing temperature on flash-sintered (Mg1/3Nb2/3)0.05Ti0.95O2 ceramics

(Mg, Nb) co-doped TiO2 colossal dielectric ceramics were successfully prepared at 1200 °C for 24 min. The effects of different electric field on phase structure, microstructure and dielectric properties have been systematically studied. All the flash sintered samples were pure rutile TiO2 structure, and no second phase was produced. With the increase of electric field, the dielectric constant (at 1 kHz) firstly increases and then decreases. When the electric field is 550 V/cm, the dielectric properties (ε′ ≈ 6.0 × 105, tanδ ≈ 0.73) of the ceramic sample are the best. Flash sintered samples were annealed at different temperatures (800–1000 °C) in order to reduce dielectric loss. As the annealing temperature increases, the dielectric constant decreases gradually. When the annealing temperature is 800 °C, the dielectric constant of the ceramic sample is about 7.1 × 104 and the dielectric loss is about 0.37 (twice reduced) at 1 kHz. Impedance spectroscopy (IS) data indicated that ceramics consist of semi-conductive grains and insulated grain boundaries. This good dielectric property was attributed to the internal barrier layer capacitance (IBLC) effect.