Rietveld analysis and Mössbauer spectroscopy studies of nanocrystalline hematite α-Fe2O3

The effect of high energy ball milling on the hematite for milling periods of times ranging from 1 to 48 h was investigated by Rietveld analysis based on XRD patterns and Mössbauer spectroscopy. An expansion of the unit cell parameters was observed. Both Scherrer method and Rietveld analysis show an evident decrease of the grain size with the increase of the milling time. Moreover, some dependence of the lattice parameters on the grain size was observed. Mössbauer spectroscopy measurements reveal that there are two kinds of particles which co-exist in the sample: nanostructured and micrometric hematite. The magnetic hyperfine field is affected by the grain size.