6533b827fe1ef96bd1286eb3

RESEARCH PRODUCT

In situ and time resolved study of the - transition in nanometric particles

N. BovetNadine MillotMarc GailhanouT. Belin

subject

DiffractionCoalescence (physics)Phase transitionChemistryMaghemiteengineering.materialCondensed Matter PhysicsSurface energySoft chemistryElectronic Optical and Magnetic MaterialsInorganic ChemistryCrystallographyX-ray crystallographyMaterials ChemistryCeramics and CompositesengineeringParticle sizePhysical and Theoretical Chemistry

description

In situ and real-time study of the {gamma} to {alpha}-Fe{sub 2}O{sub 3} transition is carried out on the H10 beamline at LURE (France). {gamma}-Fe{sub 2}O{sub 3} particles are synthesized by soft chemistry. These particles have an average diameter evaluated by X-ray diffraction of 9{+-}1nm and a specific surface area of 116m{sup 2}g{sup -1}. The size of produced {alpha}-Fe{sub 2}O{sub 3} particles is determined by in situ and time resolved X-ray diffraction measurements at different temperatures. An amazing evolution of size with time is revealed: an abrupt doubling of the {alpha}-Fe{sub 2}O{sub 3} particle size is observed whatever the heating temperature. Some assumptions are given in order to explain this phenomenon which implies at the same time surface energy, granulometric distribution and coalescence of particles. -- A brutal increase of the X-rays coherent domain sizes of the {alpha}-Fe{sub 2}O{sub 3} particles during the {gamma}/{alpha} transition at nanometric scale. Maghemite {gamma}-Fe{sub 2}O{sub 3} particles ({phi}=9{+-}1nm) were heated at 723 K. First germs (or grains) of {alpha}-Fe{sub 2}O{sub 3} were detected with a size of 2 nm.

yearjournalcountryeditionlanguage
2007-08-01Journal of Solid State Chemistry
https://doi.org/10.1016/j.jssc.2007.06.013