Structural studies of iron-doped TiO2 nano-composites by Mössbauer spectroscopy, X-ray diffraction and transmission microscopy

The iron-doped TiO2 nano-composites prepared by sol-gel method and calcined at 923 K have been investigated by means of Mössbauer spectroscopy, X-ray diffraction and transmission electron microscopy. The results indicate that TiO2 exists mainly in the form of anatase phase with a grain size of about 10-20 nm. Only about 1.5 wt% Fe incorporates into the lattice of anatase and forms a substitutional Fe0.02Ti0.98O2 solid solution for all samples. We present that a superparamagnetic α-Fe2O3 phase is produced in iron-doped TiO2 nano-composites. There is a maximum of 4.0 wt% Fe in the superparamagnetic α-Fe2O3 in the doping content of 10 wt% Fe, and the amount of ferromagnetic α-Fe2O3 increases largely with the iron-doped concentration. We propose that the Fe sites in the iron-doped TiO2 are composed of substitutional FexTi1−xO2, superparamagnetic α-Fe2O3 and ferromagnetic α-Fe2O3.