Structural evolution and dielectric properties of (Bi, Mg, Zr)-doped BaTiO3 ceramics for X8R-MLCC application

The (1-x) BaTiO3-x (0.5Bi2O3-0.67MgO-0.33ZrO2) ceramics (x = 5, 10, 15 and 20 mol%) are fabricated by a conventional solid-state method in a reducing atmosphere. All ceramics display a pure perovskite phase without any trace of secondary phase, and a phase transition from tetragonal phase to pseudo-cubic phase occurs between x = 0.1 and x = 0.15. The dielectric analysis manifests that both the dielectric constant and insulation resistivity at room temperature decrease with increasing dopants, which is mainly related to the reduction of grain boundaries. Meanwhile, high dielectric constant (∼2020) and excellent insulation resistivity (∼4.81 × 1013 ΩΩ ·cm) are obtained when x = 0.05. Besides, the temperature stability of ceramics in the high temperature region is improved with little BMZ-doping, and BMZ05 ceramic satisfies the EIA X8R standard. The complex impedance demonstrates that obvious heterogeneous interfaces and strong interface polarization are existed in ceramics. The fitted activation energy of grain boundary reflects that the long-range hopping polarization of oxygen vacancies dominates in the dielectric constant of ceramics when x < 0.1, while the short-range hopping polarization of defect dipoles dominates when x > 0.15.