In situ and time resolved study of the γ/α-Fe2O3 transition in nanometric particles

In situ and real-time study of the to alpha-Fe2O3 transition is carried out on the H10 bearnline at LURE (France). gamma-Fe2O3 particles are synthesized by soft chemistry. These particles have an average diameter evaluated by X-ray diffraction of 9 +/- 1 nm and a specific surface area of 116 m(2) g(-1). The size of produced alpha-Fe2O3 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-Fe2O3 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, gramilometric distribution and coalescence of particles. (c) 2007 Elsevier Inc. All rights reserved.