Sb dopant-induced modifications in CuO–ZnO nanocomposites: Optical, electrical and magneto-dielectric insights for optoelectronic applications

Abstract

This study involves the synthesis of CuO–ZnO nanocomposites with varying Sb doping levels (0%, 2.5%, and 5%) through a facile sol-gel process. Structural analysis via X-ray diffraction confirmed the presence of ZnO's hexagonal wurtzite phase and CuO's monoclinic phase in all samples, indicating reduced crystallinity due to doping. The average crystallite size was determined using Scherrer's formula, revealing a decrease in size with doping (33 nm, 31 nm, and 30 nm for 0%, 2.5%, and 5% Sb, respectively). Morphology and chemical composition were assessed using field emission scanning electron microscopy, and energy dispersive X-ray analysis. The optical bandgap of the Sb-doped CuO–ZnO nanocomposites was determined using a Tauc plot, resulting in values of 2.48 eV, 2.39 eV, and 2.32 eV for dopant concentrations of 0%, 2.5%, and 5%, respectively. Dielectric permittivity and tangent loss were studied across the frequency range of 100 Hz to 1 MHz at different temperatures ranging from 303 K to 723 K measured between 100 Hz and 1 MHz frequency, revealing Maxwell-Wagner-type interfacial polarization. The dielectric permittivity data reveal anomalous behavior near 673 K, shifting with doping, and is explained by thermal ionization and relaxation mechanisms. The ac conductivity, which varies with frequency, demonstrates low-frequency dispersion and is effectively described by Jonscher's power law aligned with the dielectric analysis. Magneto-dielectric measurements showed a positive effect for permittivity and a negative effect for tangent loss, which may be caused by the changes in dipole alignment. The magneto-dielectric effect was further explored by analyzing the impact of magnetic fields (0–1.5 T) on impedance spectroscopy. Nyquist plots obtained at various magnetic fields were fitted using parallel combinations of resistance-capacitor circuits. These plots were then employed to estimate the contributions of both grains and grain boundaries. Overall, the findings from this study provide a foundation for the development of multifunctional materials with tailored properties for a wide range of optoelectronic devices.