Relation of Infrared, Crystallochemical, and Morphological Properties of Al-Substituted Hematites

V. Barron1, J. L. Rendon2, J. Torrent1 and C. J. Serna3
1 Departamento de Edafología, Escuela Técnica Superior de Ingenieros Agrónomos Apdo. 3048, Córdoba, Spain
2 Departamento de Química Inorgánica, Facultad de Ciencias Avda. de Medina Azahara 9, Córdoba, Spain
3 Instituto de Físico-Química Mineral, Serrano 115 dpdo., Madrid-6, Spain

Abstract: Synthetic Al-hematites prepared from ferrihydrites, at low (∼ 100°C) and high (400° and 800°C) temperatures were studied for their morphological, crystallochemical, and infrared (IR) characteristics. Low-temperature Al-hematites had a platy morphology (the plate thickness was inversely related to amount of Al substitution), and the high temperature Al-hematites showed a poorly defined morphology due to interparticle sintering. In the low-temperature Al-hematites shifts in the IR mode frequencies were noted and could be partly explained by a shape factor that was deduced from particle morphology. The intrinsic effect of Al substitution, however, was to produce shifts of as much as 10–15 cm−1 for the highest Al substitution (∼ 16%). Similar shifts were observed for the high-temperature hematites in which morphology was not appreciably affected by Al substitution.

Key Words: Aluminum • Hematite • Infrared spectroscopy • Iron oxides • Morphology • Unit-cell parameters

Clays and Clay Minerals; December 1984 v. 32; no. 6; p. 475-479; DOI: 10.1346/CCMN.1984.0320605
© 1984, The Clay Minerals Society
Clay Minerals Society (www.clays.org)