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Stable magnesium peroxide at high pressure.

Lobanov SS, Zhu Q, Holtgrewe N, Prescher C, Prakapenka VB, Oganov AR, Goncharov AF - Sci Rep (2015)

Bottom Line: However, in exoplanets oxygen may be a more abundant constituent.Raman spectroscopy detects the presence of a peroxide ion (O2(2-)) in the synthesized material as well as in the recovered specimen.Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO.

View Article: PubMed Central - PubMed

Affiliation: Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA.

ABSTRACT
Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth's lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O2(2-)) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions.

No MeSH data available.


Related in: MedlinePlus

Electron microscope images of the extracted sample (run A2).(A) SEM micrograph. Laser-heated area is shown with a dashed circle. (B) Energy-dispersive x-ray spectroscopy image. Color intensity is proportional to the element abundance. The laser-heated area (white dashed line) has higher oxygen content. The white scale bar corresponds to 15 μm.
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f5: Electron microscope images of the extracted sample (run A2).(A) SEM micrograph. Laser-heated area is shown with a dashed circle. (B) Energy-dispersive x-ray spectroscopy image. Color intensity is proportional to the element abundance. The laser-heated area (white dashed line) has higher oxygen content. The white scale bar corresponds to 15 μm.

Mentions: Mapping the extracted sample with an energy-dispersive x-ray spectroscopy (EDS) revealed that the laser-heated area has higher oxygen content (36 ± 2 at% Mg, 64 ± 3 at% O) than the area that was not subjected to high temperatures (Fig. 5). Detailed chemical characterization, however, was not possible because unreacted MgO is mixed with the oxygen-rich phase in the laser-heated area. Nevertheless, EDS analysis provides independent evidence for MgO2 in the recovered sample.


Stable magnesium peroxide at high pressure.

Lobanov SS, Zhu Q, Holtgrewe N, Prescher C, Prakapenka VB, Oganov AR, Goncharov AF - Sci Rep (2015)

Electron microscope images of the extracted sample (run A2).(A) SEM micrograph. Laser-heated area is shown with a dashed circle. (B) Energy-dispersive x-ray spectroscopy image. Color intensity is proportional to the element abundance. The laser-heated area (white dashed line) has higher oxygen content. The white scale bar corresponds to 15 μm.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4555032&req=5

f5: Electron microscope images of the extracted sample (run A2).(A) SEM micrograph. Laser-heated area is shown with a dashed circle. (B) Energy-dispersive x-ray spectroscopy image. Color intensity is proportional to the element abundance. The laser-heated area (white dashed line) has higher oxygen content. The white scale bar corresponds to 15 μm.
Mentions: Mapping the extracted sample with an energy-dispersive x-ray spectroscopy (EDS) revealed that the laser-heated area has higher oxygen content (36 ± 2 at% Mg, 64 ± 3 at% O) than the area that was not subjected to high temperatures (Fig. 5). Detailed chemical characterization, however, was not possible because unreacted MgO is mixed with the oxygen-rich phase in the laser-heated area. Nevertheless, EDS analysis provides independent evidence for MgO2 in the recovered sample.

Bottom Line: However, in exoplanets oxygen may be a more abundant constituent.Raman spectroscopy detects the presence of a peroxide ion (O2(2-)) in the synthesized material as well as in the recovered specimen.Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO.

View Article: PubMed Central - PubMed

Affiliation: Geophysical Laboratory, Carnegie Institution of Washington, Washington, DC 20015, USA.

ABSTRACT
Rocky planets are thought to comprise compounds of Mg and O as these are among the most abundant elements, but knowledge of their stable phases may be incomplete. MgO is known to be remarkably stable to very high pressure and chemically inert under reduced condition of the Earth's lower mantle. However, in exoplanets oxygen may be a more abundant constituent. Here, using synchrotron x-ray diffraction in laser-heated diamond anvil cells, we show that MgO and oxygen react at pressures above 96 GPa and T = 2150 K with the formation of I4/mcm MgO2. Raman spectroscopy detects the presence of a peroxide ion (O2(2-)) in the synthesized material as well as in the recovered specimen. Likewise, energy-dispersive x-ray spectroscopy confirms that the recovered sample has higher oxygen content than pure MgO. Our finding suggests that MgO2 may be present together or instead of MgO in rocky mantles and rocky planetary cores under highly oxidized conditions.

No MeSH data available.


Related in: MedlinePlus