Local Structure around Iron Ions in Anatase TiO2

The local structure around iron impurity in anatase TiO2 nano-composite with different iron content (1, 2, 5 and 10 wt %) has been studied by fluorescence XAFS. The results indicate that for the sample with low iron content (1 and 2 wt %), the iron ions are incorporated into the lattice of anatase, and substitute the Ti ions. With the iron content increasing to 5 wt %, only part of iron ions enter the lattice of anatase, and the rest form α-Fe2O3 phase. As the iron content reaches 10 wt %, iron ions mainly exist in α-Fe2O3 phase. It is found that, in the (1 wt %)Fe-doped TiO2 the bond lengths of the first (Fe-O) and second (Fe-Ti) shells are RFe-O=1.97 A and RFe-Ti=3.01 A, respectively, which means that the RFe-O is only slightly larger than the first shell Ti-O bond length by 0.01 A, while the RFe-Ti is significantly smaller (0.04 A) than that of the corresponding Ti-Ti shell in anatase. These results imply that iron ions occupying the Ti sites greatly change the symmetry of the first Fe-O shell