57Fe Mössbauer study of β-FeOOH obtained in presence of Al3+ and Ti4+ ions

This paper deals with the influence of Al3+ and Ti4+ ions on the formation of akaganeite when prepared by hydrolysis of FeCl3 solutions. The products were characterized by X-ray diffraction (XRD) using Rietveld refinement, Infrared spectroscopy (FTIR) and 300 and 77 K Mössbauer spectrometry (MS). Akaganeite is the only phase being formed independent upon the type and concentration of the metallic cations. No significant variations in the hyperfine and crystallographic parameters on the akaganeite prepared in the presence of Al3+ ions with concentrations lower than or equal to 10 mol% were observed. One does conclude that the present chemical route allows only rather small amounts of Al to enter in the structure of akaganeite. On the other hand, Ti4+ affects the physical properties of akaganeite: its presence favors the decrease of the average grain sizes, the reduction of both the unit cells and the magnitude of all average hyperfine parameters and the formation of structural defects.