Electrical Properties and Dielectric Relaxation Analysis of ZnAl ₂ O ₄ @ZnO Core–Shell Heterostructures

In the present report, the electrical properties and dielectric relaxation analysis of the ZnAl2O4@ZnO (ZAO@ZO) core–shell heterostructure were investigated using impedance spectroscopy. The composite was synthesized via a coprecipitation method, ensuring uniform core–shell formation, as confirmed by XRD, FESEM, TEM, EDX, and XPS analyses. Complex impedance spectroscopy (CIS) revealed distinct contributions modeled using a three-RQ equivalent circuit configured as Rint||Qint + Rshell||Qshell+ Rcore||Qcore. The interfacial resistance exhibited the lowest activation energy (90.87 meV), followed by the ZnO shell (110.52 meV) and ZnAl2O4 core (117.64 meV), indicating thermally activated conduction. Dielectric relaxation studies demonstrated non-Debye behavior, described well by the Havriliak–Negami (H–N) model, with enhanced polarization at elevated temperatures due to space charge effects. The electric modulus analysis further confirmed hopping-dominated charge transport, with relaxation peaks shifting to higher frequencies with increasing temperature. The loss tangent (tan δ) exhibited strong frequency and temperature dependence, highlighting the role of interfacial polarization in energy dissipation. These findings provide critical insights into the electrical dynamics of ZAO@ZO heterostructures, paving the way for their applications in advanced electronics, sensors, catalysts, and energy storage devices.