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 compositi on was found to vary significantly on iron loading. For the samples calcine d at 500 or 600 degreesC, at x less than or equal to0.01, the formed ZrO2 i s a mixture of monoclinic and tetragonal structures. Only tetragonal struct ure is revealed at x greater than or equal to0.05 with the exception of Fe- 0.2/ZrO2, calcined at 500 degreesC, where new non-typically short Zr-Zr dis tances (3.29, 3.43 Angstrom) were observed. At low iron loading (less than one monolayer) Fe3+ ions were found to localize within the pre-surface laye rs of ZrO2 nanoparticles showing property of isolated ions. For greater Fe loading, iron exhibits either two-dimensional layer structure or two-phase system.