Synthesis of alpha-Fe2O3 Sphere/Rod-Like Nanostructure via Simple Surfactant-Free Precipitation Route: Optical Properties and Formation Mechanism

摘要

Sphere/rod-like alpha-Fe2O3 nanostructure were successfully synthesized by simple surfactant-free precipitation route. The as-prepared samples were characterized by X-ray powder diffraction (XRD) to determine the phase purity and the crystal structure. The lattice parameter and crystallite size of the samples have been calculated from the Rietveld analysis. The crystallite size has been compared by Scherrer's formula and Rietveld method and both method showed increase of the grain size with the increase of the calcined temperature. The crystallite size was in the range of 5-30 nm. The high resolution scanning electron microscopy (HR-SEM) analysis of the samples shows that the morphology of the nanostructures changed from nanospheres into nanorods and it was confirmed by high resolution transmission electron microscopy (HR-TEM). Energy dispersive X-ray (EDX) analysis reveals the presence of 0 and Fe elements only. The optical properties of the as-prepared nanostructures were determined by photoluminescence (PL) spectra. The band gap energy was investigated by UV-Visible diffuse reflectance spectra (DRS) and calculated by means of the Kubelka-Munk method. The band gap values are decreased from 2.26 eV to 2.17 eV as the temperature increased from 300 degrees C to 400 degrees C with increasing the crystallite size. A Vibrating Sample Magnetometer (VSM) was used to study the magnetic properties of iron oxide (alpha-Fe2O3) nanostructures. Magnetic hysteresis (M-H) loops revealed that the as-prepared alpha-Fe2O3 samples displayed ferromagnetic behavior.