Abstract (≈250 words)

A comprehensive study was conducted on the phase structure, microstructure, dielectric properties, and nonlinear current–voltage (J–E) behavior of doped CaCu₃Ti₄O₁₂ (CCTO) ceramics prepared using the conventional solid-state reaction method. The investigated compositions, including pure CCTO and Zr/rare-earth co-doped samples (Zr–Sc, Zr–Sm, Zr–Gd, and Zr–La), were sintered at 1080 °C for 8 h. X-ray diffraction analysis confirms that all ceramics crystallize in a cubic perovskite structure with the space group Im–3, indicating that the crystal structure remains stable after doping.

Microstructural observations reveal the formation of dense ceramics with a significant reduction in grain size as a result of Zr/rare-earth substitution. This grain refinement plays an important role in modifying the electrical behavior of the materials. Dielectric measurements show that the doped ceramics maintain a high relative permittivity (ε′ > 3.5 × 10³). In particular, the Zr–Sc composition exhibits excellent thermal stability, with a permittivity variation (Δε′) of less than ±15% up to 160 °C. Additionally, the dielectric loss (tanδ) is significantly reduced to 0.02 at 0.1 kHz at room temperature.

A remarkable enhancement in the breakdown electric field is also observed, reaching values more than 38 times higher than that of pure CCTO in the Zr⁴⁺/Sc³⁺ co-doped composition. Furthermore, the doped ceramics exhibit an energy efficiency exceeding 98%, demonstrating their strong potential for high-efficiency energy storage applications. These improvements in dielectric and nonlinear properties are mainly attributed to the increase in grain boundary resistance (Rgb), which is closely related to the reduction of oxygen vacancies in the doped ceramics.