Co-substituted Ni–Zn ferrite reinforced PVA nanocomposites as high-performance electromagnetic wave absorbers in the X-band region
Abstract
Cobalt-substituted nickel-zinc ferrites with the composition CoxNi1−x−yZnyFe2O4 (x = 0.2, 0.4, 0.6, and 0.8; y = 0.1) were synthesized via the sol-gel method to systematically investigate the influence of Co²⁺ substitution on their structural, morphological, optical, electrical, dielectric, and electromagnetic properties. XRD and Rietveld refinement confirmed the formation of a single-phase cubic spinel structure with space group Fd-3 m, while the crystallite size was found to be in the range of 6.2–6.9 nm. FESEM analysis revealed nearly spherical nanoparticles with homogeneous grain distribution. FTIR and Raman spectroscopic studies confirmed the characteristic metal-oxygen vibrational modes of the spinel ferrite structure, indicating the preservation of structural integrity after cobalt incorporation. UV–Visible analysis revealed composition-dependent optical band gaps in the range of 1.07–1.26 eV, demonstrating modification of the electronic structure with cobalt substitution. The electrical measurements exhibited frequency-dependent conductivity and impedance behavior, with Co0.4Ni0.5Zn0.1Fe2 O4 exhibiting the highest AC conductivity and comparatively lowest impedance among the investigated compositions. Dielectric measurements showed frequency-dependent dielectric dispersion, with the x = 0.4 composition exhibiting the highest dielectric constant, consistent with interfacial polarization effects. Furthermore, flexible PVA/ferrite nanocomposite films were fabricated by solution casting and evaluated in the 7–13 GHz X-band using a vector network analyser. The PVA/ Co0.6Ni0.3Zn0.1Fe2O4 nanocomposite exhibited the highest attenuation, with a reflection loss of approximately − 45.33 dB, indicating strong microwave absorption capability. These findings demonstrate that Co²⁺ substitution effectively tunes the structural, optical, electrical, and dielectric properties of Ni–Zn ferrites, while the fabricated PVA/ferrite nanocomposite films exhibit promising microwave attenuation characteristics in the X-band. Therefore, these materials show potential for lightweight and flexible microwave absorption applications.