Synthesis, characterization and magnetic properties of ε-Fe2O3 nanoparticles prepared by sol-gel method

Abstract

Nanoparticles of ε-Fe2O3 in an amorphous silica matrix were prepared by the sol–gel method without using a precursor. X-ray diffraction patterns reflect a completely amorphous state for the samples even after heat-treated up to 600 °C, while at higher temperatures the formation of crystalline iron oxide phases was observed. Transmission electron microscopy analysis showed a wide size distribution of nanoparticles from 3±0.5 to 46±0.8 nm. The occurrence of ε-Fe2O3 particles depends on several factors like annealing temperature, particle size and iron concentration in initial chemicals. Based on the 57Fe Mössbauer spectra, three octahedral and one tetrahedral iron site were identified for ε-phase. The optimized conditions for the preparation of ε-Fe2O3 rich sample were confirmed and ~ 90% of the ε-Fe2O3 phase was obtained with the particle size of 15±0.6 nm. The high coercivity of ~ 1.18 T at room temperature was confirmed for our nanoparticle system.