Comparative structural, dielectric and electrical studies of pure, Mg-doped, Cr-doped and co-doped CaCu3Ti4O12 electro-ceramic

This work highlights the basis for the development of novel CCTO-based dielectric materials, suitable for many applications, including as capacitors. In this study, we explored the impact of Mg and/or Cr substitutions on microstructure and dielectric characteristics of CaCu _3 − x Mg _x Ti ₄ O ₁₂ (x = 0.1,0.2, 0.3), CaCu ₃ Ti _4 − y Cr _x O ₁₂ and CaCu _2.9 Mg _0.3 Ti _4−y Cr _y O ₁₂ ceramics (y = 0.01, 0.02, 0.03). The X-ray diffraction analysis confirmed that all the synthesized samples maintained a single phase, free from impurities. The Rietveld refinement results confirm the formation of all intended phases independently of the dopant rate, with slight variations in the structural parameters. Examination of SEM images revealed that the introduction of small amounts of Mg and/or Cr during sintering disclosed similar morphology compared to pure CCTO. In particular, the CaCu _2.9 Mg _0.3 Ti _3.99 Cr _0.01 O ₁₂ composition revealed minor differences in grain size compared to pure ceramics. However, the solid solutions of formula CaCu _2.9 Mg _0.3 Ti _4−y Cr _y O ₁₂ whose percentage of Chromium is greater than 0.02 show a remarkable grain growth. The dielectric studies, conducted over a wide frequency range, showed that the co-doped ceramics exhibited impressive dielectric permittivity. Notably, the compositions CaCu _2.7 Mg _0.3 Ti ₄ O ₁₂ and CaCu _2.9 Mg _0.3 Ti _4−y Cr _y O ₁₂ show a remarkable dielectric constant with values ​​ranging from about 6.7 to 8.56 × 10 ⁴ . Furthermore, Chromium-doped ceramics also exhibit low dielectric loss, with tanδ values ranging from 0.039 to 0.05. The dual substitution greatly improved resistivity. Moreover, impedance analysis revealed good stability regardless of the Chromium content in the co-doped ceramics. The highest resistivity increases with of Chromium content. Notably, the composition with the best resistivity also presents an interesting dielectric permittivity (53060) at 1 kHz.