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Title: Unraveling the complexity of iron oxides at high pressure and temperature: Synthesis of Fe 5O 6

The iron-oxygen system is the most important reference of rocks’ redox state. Even as minor components, iron oxides can play a critical role in redox equilibria, which affect the speciation of the fluid phases chemical differentiation, melting, and physical properties. Until our recent finding of Fe 4O 5, iron oxides were assumed to comprise only the polymorphs of FeO, Fe 3O 4, and Fe 2O 3. Combining synthesis at high pressure and temperature with micro- diffraction mapping, we have identified yet another distinct iron oxide, Fe 5O 6. The new compound, which has an orthorhombic structure, was obtained in the pressure range from 10 to 20 GPa upon laser heating mixtures of iron and hematite at ~2000 K, and is recoverable to ambient conditions. The high-pressure orthorhombic iron oxides Fe 5O 6, Fe 4O 5, and h-Fe 3O 4 display similar iron coordination geometries and structural arrangements, and indeed exhibit coherent systematic behavior of crystallographic parameters and compressibility. Fe 5O 6, along with FeO and Fe 4O 5, is a candidate key minor phase of planetary interiors; as such, it is of major petrological and geo- chemical importance. Here, we are revealing an unforeseen complexity in the Fe-O system withmore » four different compounds—FeO, Fe 5O 6, Fe 4O 5, and h-Fe 3O 4—in a narrow compositional range (0.75 < Fe/O < 1.0). New, finely spaced oxygen buffers at conditions of the Earth’s mantle can be defined.« less
ORCiD logo [1] ;  [2]
  1. Univ. of Nevada, Las Vegas, NV (United States)
  2. Carnegie Inst. of Washington, Argonne, IL (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 1; Journal Issue: 5; Related Information:; Journal ID: ISSN 2375-2548
Research Org:
Univ. of Nevada, Las Vegas, NV (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA)
Country of Publication:
United States
36 MATERIALS SCIENCE; 58 GEOSCIENCES; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; high pressure; iron oxide; extreme conditions synthesis; mantle phases; redox equilibria; planetary interiors; microdiffraction
OSTI Identifier: