MR025-10
Revealing chemistry at multi-megabar pressures by means of synchrotron X-ray diffraction: Fe-O system as a case study
Wednesday, 16 December 2020: 09:06
Virtual
Elena Bykova1, Maxim Bykov2, Sergey V Ovsyannikov3, Konstantin Glazyrin4, Hans-Peter Liermann4, Stella Chariton5, Vitali B Prakapenka5, Michael Hanfland6, Leonid S Dubrovinsky7 and Alexander F Goncharov1, (1)Carnegie Institution for Science Washington, Earth and Planets Laboratory, Washington, DC, United States, (2)Howard University, Washington, DC, United States, (3)University of Bayreuth, Bayreuth, Germany, (4)DESY Deutsches Elektronen Synchrotron, Hamburg, Germany, (5)University of Chicago, Center for Advanced Radiation Sources, Chicago, IL, United States, (6)ESRF European Synchrotron Radiation Facility, Grenoble, France, (7)University of Bayreuth, Bayerisches Geoinstitut, Bayreuth, Germany
Abstract:
The structure, properties and high-pressure behavior of compounds in the Fe–O system have been extensively investigated because of their high importance in Earth sciences, solid state physics and technology. The chemical, electronic, and magnetic states of iron oxides can be strongly influenced by pressure, giving rise to unexpected chemical reactions, structural and other types of transformations.
Using methods of synchrotron powder and single-crystal X-ray diffraction in laser-heated diamond anvil cells we have studied high-pressure structural behavior and high-pressure chemistry of conventional iron oxides (FeO, Fe3O4 and Fe2O3) up to 200 GPa and temperatures over 3000 K. We observed that these oxides exhibit rich polymorphism at extreme conditions which is in significant degree governed by magnetic and electronic changes in Fe ions. Moreover, none of these oxides remain chemically stable at certain pressure-temperature conditions corresponding to Earth’s deep mantle- and core-mantle boundary, forming new compounds with unusual stoichiometry like Fe5O7, Fe13O19 and Fe25O32. Our results suggest that mixed-valence iron oxides may play a significant role in oxygen cycling between Earth reservoirs.
