Formation of Nanocrystalline ferrite: Effect of Citric Acid on Structural and Spectroscopic Properties

Nanocrystalline Co0.1Ni0.7Zn0.2Fe2O4 ferrite nanoparticles were synthesized via the sol-gel method to investigate the influence of citric acid concentration on their structural and spectroscopic properties. X-ray diffraction confirmed the formation of a single-phase cubic spinel structure with well-defined reflections corresponding to the (220), (311), (400), (422), (511), and (440) planes. The crystallite size, estimated using Scherrer's equation, was found to increase from ~7.5 nm to ~21 nm with increasing citric acid content, indicating a strong correlation between chelating agent concentration and particle growth. Lattice parameters, dislocation density, unit cell volume, hopping lengths, and bond lengths were systematically evaluated, revealing modifications in lattice strain and structural ordering. Williamson-Hall analysis further demonstrated the presence of microstrain induced by size effects and lattice imperfections, with strain values varying as a function of citric acid concentration. FTIR spectroscopy exhibited characteristic metal-oxygen stretching vibrations associated with tetrahedral and octahedral sites, validating the formation of the spinel ferrite lattice, along with minor organic residue-related bands originating from the sol-gel process. The combined structural and spectroscopic analyses confirm that citric acid plays a crucial role in controlling crystallite size, lattice strain, cation distribution, and bonding characteristics in the synthesized ferrite system. These findings highlight the importance of chelating agent concentration in tailoring the structural integrity and physicochemical behavior of Co–Ni–Zn ferrite nanoparticles for potential technological and functional applications.