Defect structure and dielectric properties of Mn-doped X8R BaTiO3-based ceramics with high permittivity: Experiments and first-principle calculations

Abstract

The comprehensive control of dielectric properties and temperature stability is the focus of BaTiO3-based ceramics with non-reducibility. For this purpose, BaTiO3–0.02MgO–0.02Y2O3–0.04CaZrO3–xMnO2(x = 0, 0.005, 0.01 and 0.015) ceramics were prepared by the solid-state method and sintered in a reducing atmosphere. When x = 1.5 mol%, high dielectric constant (ԑr ∼ 3644), large insulation resistivity (ρv ∼ 2.07 × 1011 Ω cm), and low dielectric loss (tanδ ∼ 0.011) were obtained in ceramics, which demonstrated the superior potential of current studies. The effects of multivalent Mn-ion doping on the phase transition, dielectric characteristics, and defect polarization were systematically investigated based on the experimental results and first-principle calculations. The change of dielectric properties was related to the formation of new defect dipoles ([MnTi′−YBa•] and[MnTi″−2YBa•]). According to the first-principle calculations, the deformation of ceramic structures and the nonuniform distribution of electron density lead to the weakening of chemical bonds and the enhancement of carrier transitions. The interfacial polarization associated with the long-range hopping of oxygen vacancies is the main source of high dielectric constant for Mn15 ceramic samples. Furthermore, all ceramics showed excellent temperature stability and satisfied the EIA X8R standard (−55 °C–150 °C, ΔC/C25°C ≤ ±15%), which can be explained by the “core-shell” structure. The effect of internal defect structure on polarization mode presented in this work can be applied to the study of BaTiO3-based dielectric ceramics. The results have excellent application potential in the BME-MLCC industry.