Structure of the metastable modification of iron(III) oxide

Citation
Eb. Burgina et al., Structure of the metastable modification of iron(III) oxide, J STRUCT CH, 41(3), 2000, pp. 396-402
Citations number
17
Categorie Soggetti
Physical Chemistry/Chemical Physics
Journal title
JOURNAL OF STRUCTURAL CHEMISTRY
ISSN journal
00224766 → ACNP
Volume
41
Issue
3
Year of publication
2000
Pages
396 - 402
Database
ISI
SICI code
0022-4766(200005/06)41:3<396:SOTMMO>2.0.ZU;2-B
Abstract
A new metastable modification of iron(III) oxide - protohematite - has been studied. According to the X-ray diffractogram, protohematite (R3c) is iden tified as hematite (R(3) over bar c) but characterized by other selection r ules for IR and Raman active vibrations. Protohematite does not possess mec hanical stability. The protohematite-hematite phase transition is initiated by heating above 900 degreesC, or by pressure application, or by mechanoch emical activation. The higher catalytic activity of protohematite compared to hematite may be explained by its structural features, namely, by lowered symmetry of the oxygen sublattice and by the effective tetrahedral environ ment of some iron cations.