A study on the temperature-dependent impedance spectroscopic measurements of barium titanate mixed with Mg²⁺/Ca²⁺ modified barium hard-type ferrite

In this work, (BaTiO₃)_1−x – (Ba_0.96Mg_0.02Ca_0.02Fe₁₂O₁₉)_x (where 0.0 ≤ x ≤ 1.0) composite ceramics, abbreviated (BTO)_1−x – (BaMgCaFeO)_x were prepared. The successful formation of the composites was confirmed via XRD, FE-SEM, and EDX techniques. No additional phases were identified. The surface morphology observation showed large-sized grains with platelet shapes associated with the BaMgCaFeO hexaferrite phase and smaller spherical grains associated with the BTO phase. The electrical and dielectric properties have been investigated. Impedance spectroscopy was employed to explore key parameters including ac conductivity, activation energy, dielectric constant, dielectric loss, dissipation factor, real/imaginary impedance, and Cole-Cole impedance analysis. Measurements spanned 40 to 120 °C, encompassing frequencies up to 3.0 MHz. Notably, ac conductivity adhered to the power law frequency rule for all ratios across transition temperatures. Activation energy calculations (47 to 357 meV) varied due to composition and transition temperature changes, evident in distinct two-region patterns in Arrhenius plots. Dielectric parameters exhibited considerable variation across frequency, temperature, and ratio, with unique trends for each ratio attributed to intra-grain, grain boundary effects, and ionic contributions. Changes in activation energy and dc conductivity, across ratios, stemmed from multiple conduction mechanisms, including electron hopping and ionic contributions. Cole-Cole impedance functions exhibited diverse profiles of straight lines and semicircles, dependent on temperature and ratios, emphasizing complex capacitive and resistive responses influenced by intra-grains, grain boundaries, and binary ions within the composites.