Study of microstructure and electrical heterogeneity of Ho and Mg co-doped CaCu₃Ti₄O₁₂ lead free ceramics

The current study reported influence of simultaneous doping of Mg²⁺ and Ho³⁺ on geometric and intrinsic characteristics of CaCu₃Ti₄O₁₂ ceramics. Rietveld refined XRD patterns confirmed the formation of CCTO ceramic. FESEM images demonstrated that grain growth suppressed significantly from 2.8 to 1.3 µm results in high grain boundary (GB) density with addition of Ho³⁺ in Mg²⁺ doped CCTO ceramics. The XPS studies revealed that oxygen vacancies tends to decline with presence of Cu in higher oxidation state (Cu²⁺) on successive doping of Ho³⁺ ions in host matrix. The impedance spectrum was analyzed in the frequency range of 10²–10⁶ Hz at different temperatures for all prepared samples. The results revealed that reduced grain’s geometry and higher grain boundary density had a dominant influence on the dielectric constant (ε′) and dielectric loss factor (tanδ) and can be controlled by selective concentration of Mg²⁺/Ho³⁺ ions in CCTO ceramics to make them suitable for energy storage applications.