Hydrothermal synthesis and characterization of some polycrystalline α-iron oxides

Hematite powders with distinct particle morphology were obtained by hydrothermal synthesis, in the temperature range of 160-300 degrees C. Goethite and ferric hydroxide precursors prepared by precipitation and oxidation under different reaction conditions were used. The hydrothermal reactions were developed in aqueous neutral or alkaline suspensions. In some cases additives were used as growth shape agents. By changing and controlling the reaction parameters, oxide powders with desired particle shapes (acicular, polyhedral, platelike, spherical, hexagonal) and dimensions (0.1-30 mu m) were obtained. The characteristics of hematite powders, green bodies and sintered compacts were investigated by X-ray diffraction, electron microscopy, transmission and electron conversion Mossbauer spectroscopy. The correlation between the preparation conditions and the properties of the obtained iron oxides is discussed together with their potential applications. (C) 1999 Elsevier Science Ltd and Techna S.r.l. All rights reserved.