Effect of Metal Nitrate to Fuel Ratio on the Structural, Morphological, Dielectric, Magnetic and Optical Properties of Cd2+-Doped Cobalt Ferrite Nanoparticles

Abstract

In this study, Co0.7Cd0.3Fe2O4 nanoparticles were synthesized using the sol-gel auto-combustion method by varying the metal nitrate-to-fuel (MN/F) ratio, with dextrose serving as the fuel. X-ray diffraction (XRD) analysis confirmed the formation of a single-phase cubic spinel structure. The lattice parameter initially increased with increasing MN/F ratio and subsequently decreased, whereas the crystallite size estimated using the Scherrer equation remained nearly constant at approximately 31 nm across all compositions. Fourier-transform infrared (FTIR) spectra exhibited characteristic absorption bands in the ranges of 574-548 cm–1 and 437-410 cm–1, corresponding to the metal–oxygen vibrations at the tetrahedral and octahedral sites, respectively. The Debye temperature increased as the MN/F ratio increased from 1:1.2 to 1:2, followed by a subsequent decrease. Field-emission scanning electron microscopy (FE-SEM) images revealed densely packed, predominantly spherical grains with slight agglomeration. Energy-dispersive X-ray spectroscopy (EDS) confirmed the presence of the expected constituent elements, namely cobalt, cadmium, iron, and oxygen. The dielectric properties exhibited an exponential decrease with the logarithm of frequency, with a pronounced dependence on the MN/F ratio. Furthermore, the optical band gap increased slightly from 1.78 to 1.83 eV. The saturation magnetization and related magnetic parameters increased with the MN/F ratio. These results establish the role of fuel content in modulating the structural, dielectric, optical and magnetic characteristics of Co0.7Cd0.3Fe2O4 nanoparticles.