Dielectric properties of (Bi0.5Nb0.5)xTi1-xO2 ceramics with colossal permittivity

The (Bi0.5Nb0.5)xTi1-xO2 (BNTO, 0 ≤ x ≤ 0.05) ceramics were synthesized by a standard conventional solid-state reaction. The effects of sintering temperature and composition x on the crystal structure, microstructure, and dielectric properties of BNTO ceramics were investigated. A pure rutile phase is achieved as x ≤ 0.01, and secondary phase Bi1.74Ti2O6.624 is detected as x ≥ 0.025. BNTO ceramic with x = 0.025 shows a high dielectric constant (155.1 k) and low dielectric loss (0.042) at 1 kHz (room temperature). Colossal permittivity is primarily related to Maxwell-Wagner effect, electron-pinned defect-dipoles or weak-binding electron. The low dielectric loss is argued to Bi ions which are doped into TiO2 lattice and the formation of Bi1.74Ti2O6.624 phase.