Yttrium-doped Ni–Zn ferrites: Structural evolution and multifunctional performance

The spinel ferrite Ni 0.6 Zn 0.4 Y x Fe 2-x O 4 (0.0 ≤ x ≤ 0.3) was synthesized using the sol–gel auto-combustion route utilizing sucrose as a fuel. The influence of Y ⁺3 substitution was studied in terms of structural, elastic, optical, electrical, magnetic and antibacterial activities. X-ray diffraction confirmed the formation of single-phase cubic spinel structure for all ferrite samples with lattice parameter in the range 8.296–8.305 Å. FESEM micrographs revealed agglomerated nanosized grains, while EDX analysis verifies the elemental stoichiometry of Ni, Zn, Fe, Y, and O. FTIR spectra exhibited characteristic vibrational bands around ∼576.32 cm⁻¹ and ∼420.12 cm⁻¹ corresponding to tetrahedral and octahedral metal-oxygen vibrations. The elastic moduli calculated from FTIR data showed an increasing trend with Y ⁺3 concentration, whereas Poisson’s ratio remained nearly constant. UV–Visible diffuse reflectance analysis shows a wider optical band gap ranging from 1.56 to 1.67 eV. The variation in AC conductivity with frequency followed the Maxwell–Wagner interfacial polarization mechanism, resulting from the heterogeneous grain and grain boundary structure. Magnetic measurements demonstrated an increase in coercivity with Y ⁺3 doping due to enhanced anisotropy, lattice strain and domain wall pinning, while remanent magnetization remained nearly constant, indicating a preserved sublattice magnetization balance. Antibacterial activity studied against Staphylococcus aureus and Escherichia coli bacteria may demonstrate concentration-dependent inhibition, which might improve with Y ⁺3 concentration. The enhanced antibacterial performance may be attributed to ROS generation, hence disrupting cell membranes and electrostatic interactions between the ferrite and bacterial cell walls leading to cell lysis, reduced grain size and surface reactivity at higher Y ⁺3 doping further contributes to bacterial inhibition. Overall, Y ⁺3 substitution in Ni–Zn ferrites effectively modulate the physical parameters and antibacterial behaviours, suggesting potential for antimicrobial coatings and biomedical devices.