Co-substituted Ni–Zn ferrite reinforced PVA nanocomposites as high-performance electromagnetic wave absorbers in the X-band region

Cobalt-substituted nickel–zinc ferrites with the composition CoₓNi₁₋ₓ₋ γ Zn γ Fe₂O₄ (x = 0.2, 0.4, 0.6, and 0.8; y = 0.1) were synthesized via the sol–gel method to investigate the influence of Co²⁺ substitution. XRD analysis confirmed the formation of a single-phase cubic spinel structure. Rietveld refinement further verified the crystallographic purity of the synthesized ferrites, while a systematic variation in lattice parameters was observed with increasing cobalt concentration. FESEM micrographs revealed nearly spherical nanoparticles with homogeneous grain distribution. FTIR and Raman spectroscopic studies confirmed the characteristic vibrational modes of the spinel ferrite structure, indicating the preservation of structural integrity after cobalt incorporation. UV–Visible spectroscopy showed a gradual reduction in the optical band gap from 1.45 to 1.07 eV, suggesting significant modification of the electronic structure. Electrical measurements exhibited frequency-dependent conductivity and impedance behavior, with enhanced conductivity for Co-substituted compositions. To evaluate their practical applicability, ferrite/PVA nanocomposite films were fabricated and investigated in the X-band frequency range relevant to 5G communication systems. The nanocomposites exhibited high dielectric properties and excellent electromagnetic interference shielding performance. The optimized composition demonstrated a reflection loss ranging from − 19.86 to − 45.33 dB, highlighting its strong potential for advanced microwave absorption and high-performance EMI shielding applications.