Colossal Permittivity Ti_1–x(Eu_0.5Ta_0.5)_xO₂ Ceramics with Excellent Thermal Stability

The lack of systematic investigations on composition dependence, phase structures, and microstructures impedes the full understanding of the colossal-permittivity (CP) behavior of acceptor and donor co-doped TiO2 ceramics. In this work, a system of Ti1–x(Eu0.5Ta0.5)xO2 ceramics with excellent dielectric properties (x = 0.01, εr ≈ 3.4 × 104, tanδ ≈ 0.011 at 1 kHz and 25 °C) and temperature stability (x = 0.01, Δεr/ε25 ≤ ± 15% within the temperature range from −140 to 250 °C) is designed. More importantly, the composition effect on the crystal structure, secondary phase, dielectric properties (CP and low dielectric loss), and temperature stability is researched utilizing experimental characterization and first-principles calculations. The introduction of heterogeneous ions, structural deformation, and oxygen vacancies plays a key role in optimizing the dielectric properties. In particular, the interface barrier layer capacitor (IBLC) effect induced by insulated grain boundaries and semiconductive grains is the primary cause of the CP behavior, and the dielectric loss is mainly affected by the Ta-rich secondary phase under different Ta element contents.