Pressure Dependence of the Liquidus and Solidus Temperatures in the Fe-P Binary System Determined by In Situ Ultrasonics: Implications to the Solidification of Fe-P Liquids in Planetary Cores
- Case Western Reserve Univ., Cleveland, OH (United States); Univ. of Lille (France)
- Case Western Reserve Univ., Cleveland, OH (United States)
- Univ. of Chicago, IL (United States)
We have developed a new technique for determining the liquidus and eutectic (or solidus) temperatures of Fe–light element alloys at high pressures in a multianvil apparatus, by studying ultrasonic wave propagation through the sample. While the onset of melting is manifested by the loss of both compressional (P–) and shear (S–) wave signals due to the scattering of sound waves by partial melts, the completion of melting is confirmed by the reappearance of the P wave signal when the scattering due to residual crystals disappears. By applying this technique to the Fe–P binary system with three different phosphorus contents, we were able to constrain the Fe–rich portion of the phase diagram up to 7 GPa and 1,733 K. Our results show that for phosphorus–poor compositions, ranging from Fe–5wt%P to the eutectic composition, the liquidus temperature exhibits a weak negative pressure dependence (dT/dP = –10.4 K GPa–1 for Fe–5wt%P). While for the phosphorus–richer compositions, including Fe–10wt%P and Fe3P, the liquidus temperature increases significantly with pressure (dT/dP = 71.3 and 62.5 K GPa–1, respectively). Here, this indicates a shift of the eutectic composition to lower phosphorus contents with increasing pressure. Consequently, molten metallic cores of planetary bodies with phosphorus contents ranging from Fe–5wt%P to the eutectic composition would start crystallization from the top of the core and proceed downward. Whereas cores with phosphorus–richer compositions (Fe–10wt%P to Fe3P) would undergo a bottom–up crystallization, resulting in a growing solid inner core.
- Research Organization:
- Argonne National Lab. (ANL), Argonne, IL (United States)
- Sponsoring Organization:
- USDOE; National Aeronautics and Space Administration (NASA); National Science Foundation (NSF); National Aeronautics and Space Administration
- Grant/Contract Number:
- FG02‐94ER14466; AC02‐06CH11357; EAR‐1128799; NNX14AN01G; NNX15AH31G
- OSTI ID:
- 1452858
- Journal Information:
- Journal of Geophysical Research. Planets, Vol. 123, Issue 5; ISSN 2169-9097
- Publisher:
- American Geophysical UnionCopyright Statement
- Country of Publication:
- United States
- Language:
- ENGLISH
Web of Science
Electrical Resistivity of Iron Phosphides at High‐Pressure and High‐Temperature Conditions With Implications for Lunar Core's Thermal Conductivity
|
journal | June 2019 |
High-Pressure Sound Velocity Measurements of Liquids Using In Situ Ultrasonic Techniques in a Multianvil Apparatus
|
journal | January 2020 |
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