Structural evolution, electrical properties, and non-ohmic behavior of barium-doped CaCu3Ti4O12 ceramics synthesized via solid-state method

Barium-doped calcium copper titanate ceramics Ca_1-xBa_xCu₃Ti₄O₁₂ with x = 0, 0.05, 0.1 and 0.2 were synthesized by the conventional solid-state method. We studied the effects of substituting Ca for Ba in the perovskite compound CCTO on structural evolution and electrical responses by changing the value of x. Processing the results of X-ray diffraction analysis using the Rietveld refinement method revealed that all the powders of the compounds studied in this work present a single perovskite phase with cubic symmetry of the Im $\bar{3}$ space group. SEM analysis revealed that Ba doping promotes a reduction in grain size and a more uniform grain distribution. Complex impedance analysis highlighted a marked reduction in grain boundary resistance and an increase in relaxation time with Ba substitution. Dielectric measurements shows that all the doped ceramics have a lower dielectric permittivity value (ε_r) than CCTO, due to the low grain boundary resistivity of the barium-doped compounds. AC conductivity showed frequency-dependent behavior consistent with hopping conduction mechanism, while barium doping reduced conductivity, due probably to lower carrier mobility and finer grain size. The breakdown field (E_b) and the non-linear coefficient (α) were significantly improved with Ba doping, reaching maximum values of 5.01 kV/cm and 7.45, respectively.