2006 Fiscal Year Final Research Report Summary
Density measurement and phase exploration of Fe-S compounds under the Earth's core pressure.
| Project/Area Number |
17540403
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Solid earth and planetary physics
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| Research Institution | Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology |
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Principal Investigator |
SATA Nagayoshi Independent Administrative Institution, Japan Agency for Marine-Earth Science and Technology, Institute for Research on Earth Evolution, Researcher, 地球内部変動研究センター, 研究員 (60371720)
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| Project Period (FY) |
2005 – 2006
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| Keywords | the Earth / the Earth's core / iron sulfide / high pressure experiments / equations of states |
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| Research Abstract |
The purpose of this study is to investigate stability of high-pressure Fe3S phase under the Earth's core conditions. We first try to synthesize the sample using large volume press (LVP). The synthesized sample was observed with a field emission scanning electron microscope (FE-SEM). Even if carefully eliminated vapor contamination, it has a lot of FeO bubbles and the bulk composition was shifted to more sulfur rich. As a result, Fe3S and Fe2S compounds are coexisting with FeO bubbles. Since it is difficult to pick up a pure Fe3S compounds, we changed synthesis method to using an laser heated diamond anvil cell (LHDAC). Fe and FeS mixture was heated at 25-50 GPa and 1500 K for about 30 minutes. The recovered sample was investigated with a FE-SEM. It has a more complex texture, Fe3S compound, starting Fe and FeS, intermediate Fe2S and Fe3S2 are coexisting. Synthesis with LHDAC and investigation with FE-SEM on recovered samples is very strong tool to study on phase relations of Fe-S system. However more time is needed to make a single phase for staring materials. We also try to identify the synthesized samples with synchrotron X-ray diffractions. Since starting FeS is not yet studied more than 20 GPa, we first studied on FeS using LHDAC and synchrotron X-ray. We found that FeS is transformed to new high-pressure phase (FeS VI) around 30 GPa. We continued to study on FeS instead of Fe3S. FeS VI still has a NiAs type related structure with an orthorhombic symmetry. It can be quenchable down to room temperature. It is different from known high-pressure phase (FeS II and II) have successive high-temperature phases (FeS IV and V). FeS VI is stable at least up to 180 GPa.
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