Infrared Spectroscopy Analysis of Oxyhydroxides as Intermediate Species in the Formation of Iron Oxides-Silica Xerogels

A detailed infrared spectroscopy analysis in the 2500 to 3800 cm −1 region has been used to study the formation of species in samples of iron oxides embedded in silica xerogel matrix. We report the presence of α, β, and γ forms of iron oxyhydroxides as intermediate species in the formation of α-Fe 2 O 3 , γ-Fe 2 O 3 and ε-Fe 2 O 3 starting from three different iron precursors: iron nitrate, iron chloride and nanometric Fe particles prepared by chemical reduction. Our results show that under thermal dehydration α and γ forms of iron oxyhydroxides transform into hematite and maghemite, respectively, whereas the β form transform to the ε-Fe 2 O 3 without going through an intermediate iron oxide phase.