High-pressure phase transition of hematite, Fe2O3

Structural phase transitions of iron oxide (Fe,03) have been investigated at pressures up to 70 GPa and temperatures above 2500 K, using a laser-heated diamond anvil cell technique. A phase transition between alpha-Fe2O3 (hematite) and perovskite-type Fe2O3 was observed at about 30 GPa. At pressures higher than 50 GPa, we also observed the occurrence of a new high-pressure phase of Fe2O3. Diffraction peaks of the new high-pressure phase can be indexed on the basis of orthorhombic or monoclinic symmetries that are denser than other known Fe2O3 phases. The volume change from perovskite-type to the new high-pressure phase is about 7%. (C) 2004 Elsevier Ltd. All rights reserved.