Study on the structure and reduction behaviour of the iron-zirconium oxide system

The structures and reduction behaviour of iron-zirconium oxides prepared by the coprecipitation method have been studied using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR), BET surface-area measurements and Mossbauer spectroscopy. The structure of the iron-zirconium oxides is severely affected by the composition. For iron-zirconium oxides with different iron contents, the chemical states of the Fe3+ cations are quite different, and hence the reduction behaviour of these Fe3+ cations is quite different too. The various intermediates formed during the successive reduction steps of the iron-zirconium oxides were determined using TPR combined with in situ Mossbauer spectroscopy. For the samples with low iron content (less than or equal to 20 atom%), Fe3+ cations were doped in the lattice of cubic zirconia and were difficult to reduce to Fe-O By contrast, for the samples with high iron content (much greater than 70 atom%), Zr4+ cations were doped in the lattice of alpha-Fe2O3 and the reduction of the Fe3+ cations to Fe-O was easier than that of the samples with low iron content.