Formation, morphology and composition of F−- and Cl−-stabilized iron β-oxyhydroxides

• β-Oxyhydroxides of iron by hydrolysis of FeF3 and FeCl3 salts.
• The morphology, composition and formation mechanism by SEM, TEM, XRD and XPS.
• The composition of β-FeOOH,F octahedrons by analysis of Mössbauer spectra (MS).
• The difference in the Neel temperature of β-FeOOH,F and β-FeOOH,Cl.

In this study, the composition, morphology and chemical state of elements were determined for iron β-oxyhydroxides fabricated by hydrolysis of FeF3 and FeCl3 (for comparison) salts under identical conditions. Based on the results obtained by numerous methods such as X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy and Mössbauer spectroscopy down to cryogenic temperatures it was determined that β-oxyhydroxides formed in the fluoride-containing solutions are composed of octahedra containing none or up to three F− ions. The tunnels of β-FeOOH,F are filled with HF. The formation and differences in the structure and composition of the obtained somatoids were explained in terms of hydrolysis reactions taking into account the interactions of chlorides and fluorides with iron.

The formation, morphology, composition and magnetic parameters of β-oxyhydroxides synthesized in the aqueous solutions of FeF3 and FeCl3 by hydrolysis reactions were evaluated using XRD, XPS, SEM, TEM and Mössbauer spectroscopy. Results indicated that β-FeOOH,F are composed of three octahedra differing in the contents of fluorine atoms, namely [FeO3(OH)3], [FeO3F(OH)2] and FeO3F2OH with HF trapped in the tunnel and transition Neel temperature of 250 K.Figure optionsDownload as PowerPoint slide