Investigation of the structure of protohematite - metastable phase of ferrum (III) oxide

A new modification of Fe(III) oxide - protohematite - was produced by therm al decomposition of crystalline hydroxides and salts and by plasma chemical method. Protohematite is a metastable phase which transforms into alpha-Fe 2O3 at 1100 degrees C, under pressure or mechanic chemical activation. IR a nd Raman spectroscopy, X-ray powder diffraction, and transmission electron microscopy were used to study the structure of protohematite. It was conclu ded that protohematite has unique structural characteristics. The hypothesi s concerning the structure of protohematite was suggested. Specific chemica l activity of the protohematite was assumed to originate from the presence of some ferric cations in quasi tetrahedral (distorted octahedral) coordina tion. (C) 2000 Elsevier Science B.V. All rights reserved.