The Influence of Crystallization on the Infrared Spectra of α- and γ-Ferric Oxyhydroxides

Abstract

The relationship was investigated between crystallization and infrared spectra of α- and γ-ferric oxyhydroxides (α-FeOOH, γ-FeOOH), which play an important role as the main components of iron ores and rusts. The results obtained are as follows:(1) The absorbance of the 1100 cm−1 band of α-FeOOH increases with the increases of the degree of incompleteness of its crystallization.(2) The 600 cm−1 band of α-FeOOH shifts from 610 to 643 cm−1 (The more the crystallization is, the higher the wave number shift goes). Accordingly, this absorption band should be called “the crystalline band”.(3) The three bands of α-FeOOH near 400 cm−1 (450, 400 and 372 cm−1) and of γ-FeOOH near 500 cm−1 (590, 520 and 483 cm−1) split considerably according to the progress of crystallization.(4) The absorbances of the characteristic bands of α- and γ-FeOOH are related to the half widths of those X-ray diffraction patterns.(5) The characteristic curves between the absorbance and quantity for the sample treated for different ageing periods are apparently different, because of its crystallization.