Synergistic Enhancement of Dielectric Properties in CCTO Ceramics via Zn2+ and Zr4+ Co-doping

Novel CaCu 3- x Zn x Ti 3.95 Zr 0.05 O 12 (CCZTZO, x = 0.025 - 0.1) ceramics were synthesized via a sol-gel route to optimize the intrinsic dielectric limitations of CaCu 3 Ti 4 O 12 (CCTO). Systematic investigation of Zn 2+ and Zr 4+ co-doping effects and annealing temperature variations (900 - 1050 °C) on microstructure and dielectric characteristics revealed: XRD analysis confirmed phase-pure CCZTZO crystallization with complete elimination of secondary phases after organic binder removal via re-sintering at 1000 °C. SEM and XPS characterizations validated successful dopant incorporation, demonstrating a monotonic reduction in grain size with increasing Zn 2+ content. Impedance spectroscopy revealed enhanced electrical resistance and substantially reduced dielectric loss tangent (tanδ) while maintaining high dielectric constants (ε′). Optimal performance was achieved in CaCu 2.9 Zn 0.1 Ti 3.95 Zr 0.05 O 12 (CCZTZO-4), exhibiting an low tanδ of 0.002 with high ε′ ≈ 1.27 × 10 3 . Furthermore, excellent frequency stability was observed across 10 2 Hz - 10 5 Hz, with ε′ maintained at ∼10 3 and tanδ consistently between 0.002 - 0.054. Temperature-dependent measurements revealed outstanding thermal stability with a relative permittivity coefficient Δε′/ε′ 25°C ≤ ±10 % over − 60 °C to 120 °C. Analysis of electrical modulus and impedance spectra indicated modified activation energies for both bulk and grain boundary responses, demonstrating that Zn 2+ and Zr 4+ co-doping effectively enhances the interfacial polarization mechanism in CCTO-based ceramics.