Study of uncoated and silica-coated hematite (α-Fe2O3) nanoparticles

The effect of silica (SiO2) matrix with different concentrations (i.e. x = 0, 20, 40 and 60 wt.%) on structural, morphological, optical and dielectric properties of hematite (α-Fe2O3) nanoparticles was investigated. The uncoated and silica-coated α-Fe2O3 nanoparticles were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), Fourier transform infrared (FTIR) spectroscopy. The frequency dependent dielectric properties of uncoated and silica-coated α-Fe2O3 nanoparticles were also investigated by LCR meter. The size of α-Fe2O3 nanoparticles was reduced from 18.80 nm to 16.71 nm with increasing percentage of silica matrix. The crystallinity of α-Fe2O3 nanoparticles was suppressed with increasing contents of silica due to reduced particle size and amorphous nature of silica matrix. Scanning electron microscopy (SEM) revealed spherically shaped α-Fe2O3 nanoparticles. In FTIR spectra, different bonds of hematite nanoparticles, SiOH and SiOSi were observed at 418 and 624, 859 and 1136 cm−1, respectively. The direct band gap was increased from 1.91 eV to 1.95 eV and the in-direct band gap was decreased from 1.37 eV to 1.32 eV with the increase concentration of silica. It was found that silica coating has prominent effects on structural, optical and dielectric properties of α-Fe2O3 nanoparticles.