Giant dielectric response and relaxation behavior in (Tm + Ta) co-doped TiO₂ ceramics

Dielectric materials with huge dielectric constants are attracting attention due to the growing demand for microelectronics and high energy-storage devices. In this work, Tm + Ta co-doped TiO₂ ceramics were prepared by a solid-state reaction (SSR) method, and the microstructure and dielectric behavior were investigated. A ultrahigh permittivity (ε_r ∼ 2.26 × 10⁴) and very low loss (tan δ ∼ 0.011) are achieved at 1 kHz for (Tm_0.5Ta_0.5)_0.01Ti_0.99O₂ ceramics. XPS analysis confirms that the high dielectric constant and low dielectric loss are attributed to the electron pinned defect dipole (EPDD) response formed by the coupling of Ti³⁺ and oxygen vacancies. In addition, impedance analysis and frequency dependent dielectric constant under a DC bias indicate that the presence of the internal barrier layer capacitance (IBLC) response and electrode response at low to medium frequencies (<10⁶ Hz) also contribute significantly to the dielectric constant. The findings reported in this work provide valuable insights into the simultaneous realization of a low dielectric loss and high permittivity in Tm + Ta co-doped TiO₂ ceramics and other related dielectric ceramics.