Phase relations and physical properties of iron-oxygen compounds at multimegabar pressures and high temperatures

• Applicant: Professorin Dr. Elena Bykova
• Subject Area: Mineralogy, Petrology and Geochemistry ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2018 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 406616493

The structures, properties and high-pressure and high-temperature behavior of compounds in the Fe–O system remain controversial and full of surprises despite a long history of research. Over the last decade several high-pressure iron oxides with hitherto unknown stoichiometries were discovered. These materials are very important for the geosciences (and planetary sciences) as potential phases during the Earth’s accretion, as possible components of present day mantle, and for controlling oxygen fugacity in the mantle, core mantle boundary, and in the core. Moreover, novel iron oxides, their electronic and magnetic properties are of great interest for modern solid state physics, chemistry, material sciences, and even for in the industry (as elements in switching electronics and memories).Iron oxides will be synthesized at pressures over 200 GPa and temperatures up to 3500 K and studied in situ in laser-heated diamond anvil cells (DACs) employing a range of advanced complementary techniques: X-ray diffraction (XRD), Mössbauer and Raman spectroscopy (and when applicable X-ray absorption spectroscopy and electrical resistivity measurements) and theoretical calculations. Methodological aim of the project is to extend single-crystal diffraction studies to over 200 GPa. Particular attention will be paid on studies of FeO, Fe3O4, Fe2O3, Fe4O5, Fe5O6, Fe5O7, Fe7O9, and FeO2. The ultimate goals of the project are to construct pressure-temperature-composition (P–T–X) phase diagram of Fe–O system at conditions covering entire Earth mantle and significant part of the core; analyze how pressure-temperature induced transformations in Fe–O compounds may affect geochemical processes in the Earth’s interior; reveal relations between structure, chemical bonding, and properties of different iron oxides; and formulate crystal chemical principals governing behavior of transition metal oxides at extreme conditions.

• DFG Programme: Research Grants
• International Connection: France
• Partner Organisation: Agence Nationale de la Recherche / The French National Research Agency
• Cooperation Partners: Dr. Julien Haines; Dr. Jérôme Rouquette