Structural and impedance characterization of BaBi₄Ti₄O₁₅ (BBT)–ZnO composites under temperature variation

This study explored the effects of ZnO addition (2%, 5%, and 10% by weight) on the microstructural and electrical characteristics of BaBi₄Ti₄O₁₅ (BBT) ceramic composites, synthesized by solid-state reaction and investigated in the radio frequency (RF) region. Structural characterization by X-ray diffraction with Rietveld refinement confirmed the formation of the secondary Zn₂TiO₄ phase in the composites, further corroborated by Raman spectroscopy. Scanning electron microscopy (SEM) revealed microstructures with lamellar grains and reduced porosity compared to pristine BBT, and energy-dispersive X-ray spectroscopy (EDS) confirmed the homogeneous elemental distribution. Impedance spectroscopy (IS) demonstrated a significant increase in relative dielectric permittivity (ε’r) at low frequencies, reaching maximum values for BBT with 2% ZnO (ε’r ≈ 2406 at 10 Hz), associated with the Maxwell–Wagner polarization mechanism. The AC conductivity (σAC) followed Jonscher’s law, indicating a conduction mechanism based on translational hopping. Nyquist plots exhibited asymmetric semicircles, characteristic of non-Debye relaxation, with distinct responses for grains and grain boundaries.