Hydrothermal Synthesis of Micrometric Rhombohedral Single Crystalline FeCO3

M. Chirita, M. Kiss, A. Ieta
State University of New York at Oswego, US

Keywords: hydrothermal, superparamagnetic, micrometric single crystalline FeCO3

Summary:

We present the synthesis of highly crystalline FeCO3 microparticles by hydrothermal decomposition of the Fe(III)-EDTA complex in the presence of urea, starting from Ferric Ammonium Sulfate and Na4EDTA as main precursors. Keeping the same precursor conditions we investigated the kinetics of crystalline phase transitions between 2 hours and 40 hours of autoclavation at 250ºC. After high pressure-temperature treatment time longer than 26 hours, mixed phases of FeCO3 and magnetite coexist. Decreasing the temperature to 230ºC and maintaining the same concentrations for precursors we repeated the entire synthesis and intervals between 2 hours and 26 hours. FeCO3 and hematite coexist in mixed phases between 4 hours and 26 hours at 230ºC. At 250ºC, the hematite disappears after 8 hours of autoclavation, and sometimes magnetite appears in a very small quantity to coexist with FeCO3 between 8 hours and 18 hours of autoclavation.