¹ Medical Physics Department, College of Science, Al-Karkh University of Science, Baghdad, Iraq;

² College of Engineering, Al-Karkh University of Science, Baghdad, Iraq.

* Correspondence: ghaiath.fadhil@kus.edu

Bismuth Ferrite (BiFeO₃) nanoparticles were synthesized through the sol-gel technique at 180 °C and annealed at 400, 600, and 800 °C to study the influence of thermal treatment on their structural, optical and magnetic properties. These nanoparticles have multiferroic properties at room temperature and are advantageous in a wide range of applications. The structural characterization using X-ray diffraction confirmed the rhombohedral perovskite crystal structure in all samples but with an increase in crystallite size and a decrease in X-ray density with increasing annealing temperature. The Raman spectroscopy analysis revealed vibrational modes that characteristics to BiFeO₃ with peak shifts and widening as the annealing temperature increases. The optical properties of the annealed BiFeO₃ nanoparticles showed a red shift in absorption characteristics and a decrease in the energy bandgap from 2.9 eV to 2.4 eV as a result of the enhanced crystallinity. The magnetic behavior of BiFeO₃ revealed soft magnetic characteristics and a reduction in the saturation magnetization with annealing temperature increase, reaching a value of 0.25 emu/g at 800 °C. The hysteresis loops demonstrate that BiFeO₃ nanoparticles deviate from their room temperature multiferroic behavior toward paramagnetic behavior as the annealing temperature increases. These insights are essential for BiFeO₃ nanoparticles potential use in optoelectronic and photocatalytic applications.