Synergistic optimization of nonlinear current–voltage characteristics and dielectric properties in Mg-doped CaCu₃Ti₄O₁₂-Y_2/3Cu₃Ti₄O₁₂ composites

Calcium copper titanate based ceramics with both colossal dielectric constant and nonlinear current–voltage characteristics are promising in miniaturization of electronic devices, energy storage materials and high performance capacitive devices. In this work, A novel CaCu_3-xMg_xTi₄O₁₂-Y_2/3Cu₃Ti₄O₁₂ composite ceramic is developed via solid-phase synthesis by introducing Mg²⁺. Both significantly enhanced nonlinear coefficient (7.71) and breakdown field (12.91 kV/cm) are obtained, meanwhile maintaining a high dielectric constant. Influence of Mg²⁺ doping on the microstructure, nonlinear current–voltage characteristics, Schottky barrier parameters and dielectric relaxations, are systematically investigated. The results indicate that the introduction of Mg²⁺ has a great effect on Cu precipitation, which in turn affects the donor density in depletion layers. The barrier height first decreases and then increases with the change of Mg content, leading to enhanced nonlinear current–voltage and dielectric properties. This work elaborates the relation between ceramic performance and microstructure, offering a promising method to obtain optimized CaCu₃Ti₄O₁₂ based composites.