Deficient or excessive CuO-TiO2 phase influence on dielectric properties of CaCu3Ti4O12 ceramics

The influence of the CuO–TiO₂ phase (CT) on dielectric properties of the CCTO ceramic was investigated. CaCu_XTi_YO₁₂ (CC_XT_YO) powders were prepared based on the coprecipitated method, where 2.70 ≤ x ≤ 3.30 and 3.25 ≤ y ≤ 4.75. XRD patterns confirmed the presence of CCTO and also the secondary phases as CuO, TiO₂, and CaTiO₃ for each sample and aided in its quantification. Scanning Electron Microscopy (SEM) shows secondary phases evolution in the grain boundaries, and its influence on size and morphology of the grains. Impedance spectroscopy measurements showed that the ceramics with lower amount of CuO and TiO₂ phases (CT/deficient ceramics) exhibited the highest ε′ values (2.1 × 10⁴ at 1 kHz for CC_2.9T_3.75O ceramic). Also, CT/deficient ceramics showed lower tanδ values (0.090 at 1 kHz for CC_2.9T_3.75O ceramic) than ceramics prepared with excessive CuO–TiO₂ phase (0.241 at 1 kHz for CC_3.1T_4.25O ceramics). The deficiency of CuO and TiO₂ phases associated with high percentage of CCTO and CaTiO₃ phases resulted in ceramics with the higher ε′ values.