Dielectric properties of BaTiO3-based ceramics are tuned by defect dipoles and oxygen vacancies under a reducing atmosphere

Abstract

BaTiO3-2 mol% MnYbO3-2 mol% CaZrO3-x mol Nb2O5 (x = 0, 0.3%, 0.5%, 0.7%) ceramics were successfully prepared via the conventional solid‐state method, followed by sintering in a reducing atmosphere. The effect of Nb2O5 doping on the crystal structure, micromorphology and dielectric properties of sintered samples was studied, and the correlation mechanisms between the microstructure and dielectric properties were further determined. For x = 0.5 mol%, optimal dielectric properties with high permittivity (ԑr ∼ 3570), low dielectric loss (tanδ ∼ 0.013) and large insulation resistivity (ρv ∼ 4.95 × 1011 Ω cm) are obtained. On this basis, the temperature coefficient of the capacitance (ΔC/C25°C) ranges between ±15% over the temperature range from −55 °C to 125 °C, satisfying the EIA X7R standard. Analysis shows that the increased permittivity of the doped ceramics at room temperature is due to enhanced short-range hoping polarization triggered by the formation of defect dipoles ([MnTi″−2NbTi·]× and [YbTi′−NbTi·]×) and the release of oxygen vacancies. The high insulation resistivity is related to the grain size and electron migration in the ceramics. In addition, the improvement in the temperature stability of the ceramics is ascribed to a decrease in the Curie temperature. The polarization mechanism presented in this work can be extended to BaTiO3 materials, and the results have important application value for BME-MLCC devices.