Magnetic and structural properties of pure hematite submitted to mechanical milling in air and ethanol

The mechanochemical treatment of α-Fe2O3 (hematite) powder in air and in ethanol at different times using a planetary ball mill was performed. X-ray diffraction (XRD) using Rietveld analysis and Mössbauer spectrometry showed partial transformation from α-Fe2O3 to a spinel phase for prolonged milling times in air, while only the α-Fe2O3 phase was obtained at all milling times using ethanol. Best XRD and Mössbauer fits were obtained by introducing two hematite components, one of them assigned to the precursor sample, and the other one to a nanoestructured hematite. Superparamagnetic hematites were only detected in the samples milled in air. An expansion of both a and c lattice parameters for the samples milled at all times in both environments were observed. Average grain sizes for the nanostructured hematites milled in air were always lower than those for the samples milled in ethanol at all times, reaching a minimum of about 11 nm.