Structural, morphological, optical, dielectric, electrical, magnetic, and electrochemical properties of V-doped CoFe2O4 nanoparticles synthesized by the combustion method

In this study, vanadium-doped cobalt ferrite (V:CoFe 2 O 4 ) nanoparticles with varying V concentrations (0.0 - 1.0 wt.%) were synthesized via a cost-effective flash combustion method and systematically investigated for their structural, morphological, optical, dielectric, magnetic, and electrochemical properties. X-ray diffraction (XRD) spectra confirmed the formation of a pure inverse spinel structure, with a gradual reduction in lattice parameter (from 8.36 to 8.33 Å) and crystallite size (from 29.4 to 16.2 nm) upon V doping. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses revealed agglomerated spherical nanoparticles with decreasing grain size and improved surface homogeneity. Raman and XPS studies verified successful V incorporation, accompanied by partial cation redistribution between A and B sites. Photoluminescence spectra showed emission quenching near 625 nm with increasing V content, attributed to non-radiative recombination centers. Dielectric measurements exhibited high ε′ values (∼150 - 160) and enhanced frequency stability, while AC conductivity increased at higher frequencies due to polaron hopping. Magnetic analysis indicated a non-monotonic variation in saturation magnetization (22.8–70.8 emu/g) and coercivity (920–1650 Oe), governed by crystallite size, cation migration, and V oxidation states. Notably, electrochemical testing revealed a peak specific capacitance of 234.4 F/g for 0.5 wt.% V:CoFe 2 O 4 , an 82% improvement over the undoped counterpart, highlighting its potential in spintronic and energy storage devices. These results demonstrate that controlled V-doping provides a tunable pathway to enhance the multifunctional performance of cobalt ferrite nanomaterials.