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

Nanoparticles of epsilon-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 degrees 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 epsilon-Fe2O3 particles depends on several factors like annealing temperature, particle size and iron concentration in initial chemicals. Based on the Fe-57 Mossbauer spectra, three octahedral and one tetrahedral iron site were identified for epsilon-phase. The optimized conditions for the preparation of epsilon-Fe2O3 rich sample were confirmed and similar to 90% of the epsilon-Fe2O3 phase was obtained with the particle size of 15(+/- 0.6) nm. The high coercivity of similar to 1.18 T at room temperature was confirmed for our nanoparticle system.