Colossal Permittivity Ti<sub>1–<i>x</i></sub>(Eu<sub>0.5</sub>Ta<sub>0.5</sub>)<i><sub>x</sub></i>O<sub>2</sub> Ceramics with Excellent Thermal Stability

The\nlack of systematic investigations on composition dependence,\nphase structures, and microstructures impedes the full understanding\nof the colossal-permittivity (CP) behavior of acceptor and donor co-doped\nTiO<sub>2</sub> ceramics. In this work, a system of Ti<sub>1–<i>x</i></sub>(Eu<sub>0.5</sub>Ta<sub>0.5</sub>)<i><sub>x</sub></i>O<sub>2</sub> ceramics with excellent dielectric properties\n(<i>x</i> = 0.01, <i>ε<sub>r</sub></i> ≈\n3.4 × 10<sup>4</sup>, tanδ ≈ 0.011 at 1 kHz and\n25 °C) and temperature stability (<i>x</i> = 0.01, <i>Δε</i><sub>r</sub>/<i>ε</i><sub>25</sub> ≤ ± 15% within the temperature range from −140\nto 250 °C) is designed. More importantly, the composition effect\non the crystal structure, secondary phase, dielectric properties (CP\nand low dielectric loss), and temperature stability is researched\nutilizing experimental characterization and first-principles calculations.\nThe introduction of heterogeneous ions, structural deformation, and\noxygen vacancies plays a key role in optimizing the dielectric properties.\nIn particular, the interface barrier layer capacitor (IBLC) effect\ninduced by insulated grain boundaries and semiconductive grains is\nthe primary cause of the CP behavior, and the dielectric loss is mainly\naffected by the Ta-rich secondary phase under different Ta element\ncontents.