EXAFS study of the Fe_x/ZrO₂ composite nanomaterials obtained by sol–gel synthesis

The local Zr and Fe arrangements in the nanocomposite system Fe_x/ZrO₂ (x=0-0.2) obtained by sol-gel method were studied by EXAFS. The phase composition was found to vary significantly on iron loading. For the samples calcined at 500 or 600°C, at x≤0.01, the formed ZrO₂ is a mixture of monoclinic and tetragonal structures. Only tetragonal structure is revealed at x≥0.05 with the exception of Fe_0.2/ZrO₂, calcined at 500°C, where new non-typically short Zr-Zr distances (3.29, 3.43Å) were observed. At low iron loading (less than one monolayer) Fe³⁺ ions were found to localize within the pre-surface layers of ZrO₂ nanoparticles showing property of isolated ions. For greater Fe loading, iron exhibits either two-dimensional layer structure or two-phase system.