Stabilization of the high coercivity image phase in the image nanocomposites

We have investigated the processes leading to the formation of the Fe2O3 and CeO2 nanoparticles in the SiO2 matrix in order to stabilize the ϵ-Fe2O3ϵ-Fe2O3 as the major phase. The samples with two different concentrations of the Fe were prepared by sol–gel method, subsequently annealed at different temperatures up to 1100 °C, and characterized by the Mössbauer spectroscopy, Transmission Electron Microscopy (TEM), Powder X-ray Diffraction (PXRD), Energy Dispersive X-ray analysis (EDX) and magnetic measurements. The evolution of the different Fe2O3 phases under various conditions of preparation was investigated, starting with the preferential appearance of the γ-Fe2O3γ-Fe2O3 phase for the sample with low Fe concentration and low annealing temperature and stabilization of the major ϵ-Fe2O3ϵ-Fe2O3 phase for high Fe concentration and high annealing temperature, coexisting with the most stable α-Fe2O3α-Fe2O3 phase. A continuous increase of the particle size of the CeO2 nanocrystals with increasing annealing temperature was also observed.