Synthesis of Iron Oxide Nanoparticles by Sol–Gel Technique and Their Characterization

Fe
₂
O
₃
nanoparticles are synthesized chemically by sol-gel method. The nanoparticles have been characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), thermo gravimetric analysis/differential thermal analysis-differential scanning calorimetry (TGA/DTA-DSC), and vibrating sample magnetometer (VSM). XRD results identify hematite phase of iron oxide nanoparticles. The average crystalline size of the nanoparticles increased from 34 to 36.7 nm when the annealing temperature increased from 400 °C to 1000 °C. FTIR technique also confirmed XRD results. Phase transformation temperatures were determined by DSC-TGA. The exothermic peak at 720.2 °C is attributed to the phase change from y Fe
₂
O
₃
(low temperature phase) to α Fe
₂
O
₃
(high temperature phase). The annealing temperature also affects the optical properties since the measured band gap increased from 2.4 to 2.7 eV when the annealing temperature increased from 400 to 1000 °C.