Quantitative Determination of Titanium Lattice Defects and Solid-State Reaction Mechanism in Iron-Doped TiO2 Photocatalysts

Iron-doped titania photocatalysts with different iron contents were prepared by using a sol−gel method in acidic media. The crystalline structures of the various phases calcined at temperatures ranging from 70 to 800 °C were studied by using the Rietveld technique in combination with XRD experiments. The average crystallite size of the phases, lattice cell parameters, phase concentrations, and titanium cationic defects in the crystalline structures of different samples were quantitatively determined. Both iron content and calcination temperature strongly affected phase transformation and solid-state reaction mechanism. Below 400 °C of calcination, all the samples had some brookite and a majority of anatase phase. Iron ions were uniformly distributed in the interstices of titania crystals to form a titanium−iron solid solution when the samples were calcined at 80, 200, and 400 °C. However, when the temperature was 800 °C, Fe2TiO5 was produced in the sample containing 5 wt % Fe by a reaction between interst...