High-Performance Giant Dielectric Properties of Cr³⁺/Ta⁵⁺ Co-Doped TiO₂ Ceramics

The effects of the sintering temperature on microstructures, electrical properties, and dielectric response of 1%Cr³⁺/Ta⁵⁺ co-doped TiO₂ (CrTTO) ceramics prepared using a solid-state reaction method were studied. The mean grain size increased with an increasing sintering temperature range of 1300-1500 °C. The dielectric permittivity of CrTTO ceramics sintered at 1300 °C was very low (ε' ∼198). Interestingly, a low loss tangent (tanδ ∼0.03-0.06) and high ε' (∼1.61-1.9 × 10⁴) with a temperature coefficient less than ≤ ±15% in a temperature range of -60 to 150 °C were obtained. The results demonstrated a higher performance property of the acceptor Cr³⁺/donor Ta⁵⁺ co-doped TiO₂ ceramics compared to the Ta⁵⁺-doped TiO₂ and Cr³⁺-doped TiO₂ ceramics. According to a first-principles study, high-performance giant dielectric properties (HPDPs) did not originate from electron-pinned defect dipoles. By impedance spectroscopy (IS), it was suggested that the giant dielectric response was induced by interfacial polarization at the internal interfaces rather than by the formation of complex defect dipoles. X-ray photoelectron spectroscopy (XPS) results confirmed the existence of Ti³⁺, resulting in the formation of semiconducting parts in the bulk ceramics. Low tanδ and excellent temperature stability were due to the high resistance of the insulating layers with a very high potential barrier of ∼2.0 eV.