The formation of maghemite γ-Fe2O3 nanoparticles was studied via in situ X-ray powder diffraction. The maghemite was formed by thermal decomposition of an amorphous precursor compound made by reacting lauric acid, CH3(CH2)10COOH with Fe(NO3)3▪9H2O. It was shown that cubic γ-Fe2O3 was formed directly from the amorphous precursor and that vacancy ordering began about 0.75h later at 305C; resulting in a tripled unit cell along the c-axis. The kinetics of grain growth were found to obey a power-law with growth exponents of 0.136 and 0.103 at 305 and 340C, respectively. Particles with average sizes of 12 and 13nm were obtained within 86 and 76min at 305 and 340C, respectively. The structure of cubic and vacancy ordered phases of γ-Fe2O3 was studied at 305C by means of Rietveld refinement.

Formation of γ-Fe2O3 Nanoparticles and Vacancy Ordering - an in situ X-ray Powder Diffraction Study. J.E.Jørgensen, L.Mosegaard, L.E.Thomsen, T.R.Jensen, J.C.Hanson: Journal of Solid State Chemistry, 2007, 180[1], 180-5