Structural, dielectric, and impedance spectroscopy studies of Zr-doped BaTiO₃ ceramics for advanced energy applications

The structural, dielectric, impedance, and electrical transport properties of Zr-doped BaTiO₃ ceramics, Ba(ZrₓTi₁₋ₓ)O₃ (x = 0, 0.20, 0.25, and 0.30), synthesized via the sol–gel method, were systematically investigated. X-ray diffraction analysis combined with Rietveld refinement confirmed the formation of a phase-pure perovskite structure for all compositions, exhibiting a tetragonal P4mm average symmetry. A progressive decrease in tetragonality with increasing Zr content was observed, indicating increasing structural distortion and a gradual tendency toward a pseudo-cubic-like state. Dielectric measurements performed over the frequency range of 1 kHz – 2 MHz and temperatures up to 600 °C revealed pronounced frequency dispersion and diffuse dielectric behavior. The highest dielectric permittivity (∼4000) was obtained for undoped BaTiO₃, while Zr incorporation systematically modified the polarization dynamics and dielectric loss characteristics. Impedance spectroscopy analysis revealed temperature-dependent non-Debye relaxation behavior arising from the coupled contributions of grains and grain boundaries. The AC conductivity exhibited frequency-dependent behavior consistent with Jonscher’s universal power law and showed a systematic reduction with increasing Zr concentration, indicating suppressed charge transport and enhanced insulating characteristics. Field-emission scanning electron microscopy (FESEM) revealed a progressive evolution of the microstructure with Zr substitution, characterized by grain growth and composition-dependent porosity variations. The observed microstructural changes correlate closely with the dielectric and electrical responses, highlighting a strong structure–property relationship. Overall, Zr substitution provides an effective approach for tailoring the structural, microstructural, dielectric, and electrical transport properties of BaTiO₃ ceramics, highlighting their potential for advanced dielectric, capacitor, and energy-storage applications.