Raman spectra and X-ray diffraction of tuite at various temperatures

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Recent advances of high-pressure generation in a multianvil apparatus using sintered diamond anvils

The tried and tested multianvil apparatus has been widely used for high-pressure and high-temperature experimental studies in Earth science. As a result, many important results have been obtained for a better understanding of the components, structure and evolution of the Earth. Due to the strength limitation of materials, the attainable multianvil pressure is generally limited to about 30 GPa (corresponding to about 900 km of the depth in the Earth) when tungsten carbide cubes are adopted as second-stage anvils. Compared with tungsten carbide, the sintered diamond is a much harder material. The sintered diamond cubes were introduced as second-stage anvils in a 6–8 type multianvil apparatus in the 1980s, which largely enhanced the capacity of pressure generation in a large volume press. With the development of material synthesis and processing techniques, a large sintered diamond cube (14 mm) is now available. Recently, maximum attainable pressures reaching higher than 90 GPa (corresponding to about 2700 km of the depth in the Earth) have been generated at room temperature by adopting 14-mm sintered diamond anvils. Using this technique, a few researches have been carried out by the quenched method or combined with synchrotron radiation in situ observation. In this paper we review the properties of sintered diamond and the evolution of pressure generation using sintered diamond anvils. As-yet unsolved problems and perspectives for uses in Earth Science are also discussed

Electrical Resistivity of Iron Phosphides at High-Pressure and High-Temperature Conditions With Implications for Lunar Core's Thermal Conductivity

Based on cosmochemistry evidence and element partitioning experiments, phosphorus is thought to be present in the iron-rich cores of Earth and Moon. Phosphorus has a similar effect as silicon and sulfur on the electrical and thermal transport properties of iron at core conditions. However, the magnitude of the impurity scattering caused by phosphorus, the temperature dependence of iron phosphorus compounds, and the change across melting all have not been intensively investigated. We measured the electrical resistivity of Fe3P, Fe2P, and FeP using a four-wire method at 1.3 to 3.2 GPa and temperatures up to 1800 K. We also identify the melting temperatures of FeP, Fe2P, and Fe3P by sudden changes in resistivity upon heating. The present experimental results demonstrate that phosphorus can enhance the electrical resistivity of iron more effectively than silicon. The resistivity of iron phosphides decreases with increasing pressures and decreasing phosphorus content. The resistivity of Fe-P alloys obeys the Matthiessen's rule, which describes the positive linear correlation between resistivity and phosphorus content. This finding is comparable to previously observed atomic order-disorder in Fe-Si and Fe-C systems. Furthermore, the resistivity of liquid Fe2P and Fe3P shows a negative linear correlation with temperatures. Different from pure iron, the calculated thermal conductivity of Fe3P increases by 33% upon melting. It is speculated that the thermal conductivity of the lunar solid inner core may be much lower than that of the liquid outer core when ordered iron light element compounds (e.g., Fe3C and Fe3P) are present in the solid core

Raman spectroscopic study of stronadelphite Sr-5(PO4)(3)F at various temperatures

The Raman spectra of stronadelphite, Sr-5(PO4)(3)F, were investigated in the temperature range of 80-1023 K at ambient pressure. No phase transition was observed though some vibrations merge or disappear during heating in this study. With increasing temperature the Raman shifts of all observed bands for Sr-5(PO4)(3)F continuously decrease. The quantitative analysis of temperature dependences for the Raman active PO4 internal modes indicates that the v(3) and v(1) stretching vibrations have larger absolute temperature coefficients (from -1.18 x 10(-2) to -1.46 x 10(-2)cm(-1) K-1) whereas the v(4) and v(2) bending vibrations show smaller absolute temperature coefficients (from -0.08 x 10(-2) to -0.90 x 10(-2) cm(-1) K-1), which may be attributed to the structural evolution of PO4 tetrahedron in Sr-5(PO4)(3)F at high temperature. The temperature and pressure dependence of the force constant for P-O stretching modes in Sr-5(PO4)(3)F were calculated. The isobaric mode Gruneisen parameters were determined as 0.046-0.365 with an average of 0.252, and the anharmonic mode parameters as -0.28 similar to 1.55 with an average of 0.33. The nonzero anharmonic mode parameters indicate an intrinsic anharmonicity for stronadelphite Sr-5(PO4)(3)F

The phase diagram of the Fe-P binary system at 3 GPa and implications for phosphorus in the lunar core

Phosphorus is a potential candidate in the metallic core of the Moon. The phase diagram of the Fe-P binary system was investigated at the pressure of 3 GPa and temperatures of up to 1600 degrees C. Up to 3.0 wt% and 10.4 wt% phosphorus can dissolve in the solid iron and liquid Fe-P phases at 1100 degrees C and 3 GPa, respectively. The eutectic temperature on the iron-rich side was determined as 1085 degrees C at 3 GPa. The solubility of phosphorus in the iron decreases from similar to 1.4 wt% at 1100 degrees C to similar to 0.7 wt% at 1500 degrees C and 3 GPa. Structure of the solid iron in the quenched sample is the body-center cubic, corresponding to alpha-Fe phase. Extending the phosphorus solubility in the solid iron to the present lunar core conditions yields a maximum phosphorus concentration in a fully crystallized iron core of 0.85 +/- 0.15 wt%. If there are Ni and C in the core, the value would be depressed to 0.4 +/- 0.1 wt%. In addition, based on a simple siderophile mass balance between the bulk Moon (BM) and bulk silicate Moon (BSM) and a modeled phosphorus partition coefficient, D-P-Moon(core/mantle) (40-200) for the lunar magma ocean, a bulk silicate Earth-like P content (82 +/- 8 ppm) in the initial Moon yields a lunar core with <0.3 wt% P. Some other potential light elements such as S and C could reduce the P content in the lunar core. Furthermore, the partition coefficient of phosphorus in the iron and liquid melt (D-p(SM/)LM) was found to be 0.10 +/- 0.03 at 3 GPa. Taking the sulfur into account, the D s p m / Lm increase to 0.18 +/- 0.02 at 5 GPa in the S-rich liquid metal (similar to 8 wt%). In the case of a solid lunar inner core and S-bearing liquid outer core, their P contents were assessed to be less than 0.09 +/- 0.01 wt% and 0.51 +/- 0.01 wt%, respectively, when the lunar core's storage of P is <0.3 wt%. The moderate phosphorus solubility in the solid iron, combined with the assumption of abundant phosphorus in the bulk Moon, indicates that the phosphorus concentration in the lunar core could higher than previously thought. (C) 2019 Elsevier Ltd. All rights reserved

Raman spectroscopic study of stronadelphite Sr-5(PO4)(3)F at various temperatures

The Raman spectra of stronadelphite, Sr-5(PO4)(3)F, were investigated in the temperature range of 80-1023 K at ambient pressure. No phase transition was observed though some vibrations merge or disappear during heating in this study. With increasing temperature the Raman shifts of all observed bands for Sr-5(PO4)(3)F continuously decrease. The quantitative analysis of temperature dependences for the Raman active PO4 internal modes indicates that the v(3) and v(1) stretching vibrations have larger absolute temperature coefficients (from -1.18 x 10(-2) to -1.46 x 10(-2)cm(-1) K-1) whereas the v(4) and v(2) bending vibrations show smaller absolute temperature coefficients (from -0.08 x 10(-2) to -0.90 x 10(-2) cm(-1) K-1), which may be attributed to the structural evolution of PO4 tetrahedron in Sr-5(PO4)(3)F at high temperature. The temperature and pressure dependence of the force constant for P-O stretching modes in Sr-5(PO4)(3)F were calculated. The isobaric mode Gruneisen parameters were determined as 0.046-0.365 with an average of 0.252, and the anharmonic mode parameters as -0.28 similar to 1.55 with an average of 0.33. The nonzero anharmonic mode parameters indicate an intrinsic anharmonicity for stronadelphite Sr-5(PO4)(3)F

Effect of temperature on the Raman spectra of Ca-5(PO4)(3)F fluorapatite

The effect of temperature on the vibrational modes of fluorapatite, Ca-5(PO4)(3)F, were investigated by micro-Raman spectroscopy in the temperature range of 80-1023K at ambient pressure. No phase transition was observed during heating though two vibrations become unresolvable due to weak intensity or overlapping. The Raman frequencies of all observed bands for fluorapatite continuously decrease with increasing temperature. The quantitative analysis of temperature dependences of Raman bands indicates that the v(3) asymmetric stretching vibrations show larger temperature coefficients (from -1.34 x 10(-2) to -1.82 x 10(-2) cm(-1) K-1) whereas the v(4) and v(2) bending vibrations have smaller temperature coefficients (from -0.27 x 10(-2) to -0.85 x 10(-2) cm(-1) K-1), which may be attributed to the temperature-induced structural evolution of the PO4 tetrahedron in fluorapatite at high temperature. The temperature and pressure dependence of the force constant for P-O stretching vibrations in Ca-5(PO4)(3)F was calculated. The isobaric mode Gruneisen parameters and anharmonic mode parameters were calculated, indicating the existence of intrinsic anharmonicity for fluorapatite