Synthesis and comprehensive investigation of ZnCoFe2O4 nanoferrite: unveiling SiO2 nanoparticle substitution effects on structural, morphological, and magnetic properties

In this study, Zn_0.5Co_0.5Fe₂O₄ spinel nanoferrites were synthesized via a conventional sol–gel combustion method at varying calcination temperatures (as-burnt, 500, 600, and 700 °C). Nanocomposites of the formula _100-x(Zn_0.5Co_0.5Fe₂O₄) + _x(SiO₂) were then prepared by substituting these ferrite nanopowders with amorphous SiO₂ nanoparticles at different concentrations (x = 0, 2, 4, 6, and 8 wt.%). This blend was homogenized in a ceramic mortar for one hour for uniform component distribution. X-ray diffraction confirmed the formation of Zn_0.5Co_0.5Fe₂O₄ nanoferrite with the \(Fd\overline{3 }m\) space group, showing crystallite size increases from 5.21 nm at as-burnt to 46.31 nm at 700 °C. SiO₂ substitution increased crystallite sizes from 36.25 nm to 49.05 nm as SiO₂ content rose from 0% to 8 wt.% in nanoferrite samples calcined at 600 °C. Fourier Transform Infrared Spectroscopy analysis identified absorption bands characteristic of the cubic spinel structure in both calcined and SiO₂-substituted samples, showcasing structural adjustments due to calcination and SiO₂ substitution. Field Emission Scanning Electron Microscopy revealed that particle sizes increased from 13.23 nm to 51.00 nm with calcination and further changed with SiO₂ incorporation, affecting the ferrite matrix microstructure and resulting in particle size increases from 42.77 nm to 52.92 nm with 2% to 8% SiO₂. Magnetic properties generally improved, displaying increased saturation and remanent magnetization, albeit with decreasing coercivity with temperature except at 700 °C. However, SiO₂ substitution led to reduced saturation and remanent magnetization and varied coercivity, peaking at a 4% SiO₂ level. These structural and ferromagnetic changes suggest significant potential for biomedical applications in the nanocomposites.