The Effect of Degree of Crystallinity on the Infrared Spectrum of Hematite

Abstract

Hematite, α-Fe2O3, one of the most abundant forms of iron oxides in this planet, has been studied and used since ancient times. A search through the pertinent literature reveals many discrepancies on the location of the characteristic IR absorption bands, in the low frequency region (<600 cm−1), which could be used as fingerprints in the identification of hematite. For example, McDevitt and Baun characterize hematite by maxima at 325, 370, 468, and 560 cm−1. Liese, however, locates absorption bands at 312, 391, 449, and 532 cm−1. Schwertmann and Taylor locate them at 345, 470, and 540 cm−1 whereas Bogdanovich et al. assign bands at 475, 520, and 580 cm−1 as characteristic for hematite. It seems that in addition to isomorphous substitution and impurities, crystal defects and the degree of crystallinity may also cause the differences in the locations of the absorption bands. The present work was undertaken to examine the latter assumption and to determine whether IR spectroscopy can be applied to distinguish between well and poorly crystalline hematites.