Synthesis of hematite and iron oxyhydroxide nanocrystals by precipitation of Fe3+ ions inside oleic acid micelles

α-Fe2O3 nanospheres with diameters of 20–40 nm and FeOOH nanorods with diameters of 150–200 nm and lengths of 0.5–1.0 μm were synthesized via hydrolysis of Fe(NO3)3 and FeCl3 solutions, respectively, in the presence of urea and oleic acid, under reflux at temperature ∼90 °C for 8 h. The molar ratio of Fe3+ ions and urea were changed until pure phases have been obtained. The key parameter of the synthesis which provides pure hematite and β-FeOOH phases was the pH. The samples were characterized by X-ray powder diffraction, transmission electron microscopy and Mössbauer spectroscopy.