Dependence of Fe Doping and Milling on TiO2 Phase Transformation: Optical and Magnetic Studies

Five weight percent of Fe-doped TiO2 nanoparticles were prepared via ball milling route. The effect of both doping and milling on the evolution of structure and microstructure alongside with optical and magnetic properties was investigated. XRD analysis revealed the coexistence of all TiO2 phases, namely anatase, brookite, and rutile with a signature of Fe cluster; meanwhile, the phase ratio changed with milling time and the dissolution of Fe dopant within TiO2 lattice. The crystallite size varies in the range of 26–44 nm with a minimum value achieved for 10 h of milling. FTIR spectroscopy confirmed the presence of characteristic functional groups belonging to TiO2 phase. The agglomeration of Fe/TiO2 nanopowders into large clusters was observed. Raman analysis showed a variation in peak positions and broadening as function of milling time and subsequently Fe doping level. UV–Vis spectroscopy manifested an increase in the absorption accompanied with a red shift and a decrease in the band gap energy from 2.57 to 2.28 eV. A strong ferromagnetic behavior was achieved, where the saturation magnetization was found to increase considerably in the range 18.1–40.15 emu/g. The appearance of ferromagnetism was associated with the dissolution of Fe with strong magnetic moment within TiO2 host lattice as well as the presence of Fe metal for longer milling.