Enhanced Functional Performance of Co-Ni-Zn Ferrites: Structural Stability, Bandgap Reduction, and Electrical Conductivity

This study presents the synthesis of Nickel-substituted Cobalt–Zinc ferrites with the chemical formula Co y Ni x Zn(1–y–x)Fe 2 O 4 (y = 0.2; x ranging from 0.1 to 0.7) using the sol–gel technique. The primary objective was to examine the effect of Ni 2+ incorporation on the structural, optical, and electrical characteristics of the materials. X-ray diffraction examination confirmed the establishment of a single-phase cubic spinel structure, with a reduction in lattice parameters attributed to the smaller ionic radius of Ni 2+ associated with Zn 2+ . Crystallographic stability across all compositions was further verified through Rietveld refinement. FE-SEM micrographs revealed uniformly distributed, nearly spherical nanograins, while FTIR and Raman analyses identified characteristic spinel vibrational modes, confirming the preservation of structural integrity following nickel substitution. The analysis by UV–Vis showed a reduction in the optical band gap from 1.53 eV - 1.26 eV, which indicated electronic transitions in the enhanced state. Dielectric and impedance studies demonstrated frequency-dependent responses, with Ni 2+ doping improving electrical conductivity through facilitated electron hopping. These results demonstrate that Ni 2+ substitution effectively tunes the structural and functional properties, making these nanoferrites promising for EMI shielding, sensors, and high-frequency device applications.