In this paper we present a study regarding the obtaining of iron oxides embedded in silica matrix, using a modified sol-gel
method. This method consists in the formation, inside the silica matrix, of some Fe(III)-carboxylate compounds, resulted in
the redox reaction between Fe(NO3)3 and diol.
We have synthesized four gels, starting from tetra-ethyl orthosilicate, Fe(NO3)3·9H2O and different diols: ethylene glycol, 1,2-propanediol, 1,3-propanediol and 1,4-butanediol, for a final composition 50% Fe2O3/50% SiO2. The obtained gels have been thermally treated at 130°C, when the redox reaction Fe(NO3)3-diol took place with formation of the precursors in the xerogels pores. The thermal decomposition of all four precursors
took place up to 300°C.
The samples obtained by annealing at 300, 500, 700°C of the four xerogels lead to crystalline phases inside the amorphous
silica matrix. γ-Fe2O3/SiO2 may be obtained as unique phase depending on the diols nature. The formation of the precursors inside the silica matrix and
the evolution of the crystalline phases were analyzed by thermal analysis, FTIR spectrometry and XRD.