302 / 2019-02-20 11:00:35

Novel oxygen-rich materials under extreme conditions

High Pressure,Pyrite phase,FeO2,FeO2Hx

全体主题 > High Pressure Physics and Materials Science

Oxygen-rich materials like peroxides and superoxides are often found in alkali metal oxides or alkaline-earth metal oxides due to the small cation to anion radius ratio at ambient. The recently synthesized pyrite-type FeO2 at high pressure suggested a novel oxygen-rich stoichiometry. FeO2 is likely to influence redox equilibria inside Earth by storing 33% more oxygen than hematite.
Herein, combining in-situ x-ray diffraction experiments and first-principles calculations, we investigated the general mechanism to imbue oxygen into conventional oxygen saturated materials like Fe2O3. In order to synthesize superoxide, oxygen channels are built in between the perovskite-Fe2O3 and the pyrite-FeO2 phases. Free oxygen atoms can readily diffuse into the perovskite-type lattice of Fe2O3, leading to stabilization of O-O bonds in FeO2. The formation of O-O bonds in FeO2 is enforced by external stress and such bonding is only kinetically stable under high pressure. This provides a general mechanism of adopting oxygen to O saturated crystal structure and produce unconventional stoichiometries. Our results also provide a feasible way of enriching oxygen in the pyrite-type phases in Earth's interiors.