Comparative study of the impact of heat treatment on the microstructure, morphology, optical and dielectric properties of nanostructured Co–Mn ferrite

Abstract

Nanoscale materials are attracting a great deal of attention due to their exceptional properties, making them indispensable for many advanced applications. Among these materials, spinel ferrites stand out for their potential applications in electronic, optoelectronic, energy storage and other devices. This is why the development of a synthesis process combined with rigorous optimization of annealing conditions is provided to be an essential approach to control nanoparticle formation and fine-tuning their structural, morphological and functional characteristics. A new approach is proposed to tailor the multifunctional properties of cobalt–manganese ferrites by synthesizing a non-stoichiometric composition. The compound Co_0.33Mn_0.33Fe_2.33O₄, containing an excess of Fe in the B sites, was obtained by the coprecipitation method combined with controlled annealing treatments. This strategy allows for the synergistic adjustment of structural, morphological, optical, and dielectric properties, and establishes a direct link between microstructural evolution and improved device performance. X-ray diffraction analysis confirmed the formation of a single-phase cubic spinel phase. The average crystallite size increased from 28 nm to 31 nm with higher annealing temperatures, indicating improved crystallinity. Morphological analysis by scanning electron microscopy revealed a significant grain growth and a reduction in irregular grain boundaries, which can minimize charge carrier scattering (beneficial for high-frequency capacitor and microwave device applications). UV-visible-near infrared spectroscopy showed a decrease in the optical band gap from 3.13 eV to 2.45 eV with increasing temperature, indicating a change in electronic structure. This variation suggests that the material can be integrated into devices such as transistors, modulators or optical switches. Finally, dielectric measurements revealed a high dielectric constant with low losses, underlining the potential of this material for applications in high-performance components.