Synthesis, reactivity, and cations inversion studies of nanocrystalline MnFe2O4particles

Nanocrystalline MnFe2O4 particles were synthesized by using citrate precursor technique. Thermal decomposition of the precursor was studied by using TGA, DTG, DTA techniques. The decomposition products were characterized by gas and chemical analyses, IR, NMR, and XRD techniques. There are three major steps that involve in the decomposition process. The dehydration step, formation of intermediate acetonedicarboxylate complex and subsequent decomposition of acetonedicarboxylate to the stoichiometric, single phase MnFe2O4 at 350degreesC with the evolution of H2O, acetone, CO and CO2 gases. The XRD crystallite size was found to be 7.0 nm and the surface area for this sample was measured to be 98.0 m(2) g(-1). Electron micrographs confirmed the nanostructured nature, spherical morphology and showed 11 nm aggregates of particles. Thermal analysis studies of nanocrystalline MnFe2O4 particles indicate the higher degree of inversion and at 380degreesC confirmed the irreversible rearrangement of Mn2+ cations from the octahedral site to tetrahedral site, that is associated with small a heat change. (C) 2002 Elsevier Science B.V. All rights reserved.