Determination of the phase boundary of GaP using <i>in situ</i> high pressure and high-temperature X-ray diffraction

Ono, Shigeaki; Kikegawa, Takumi

doi:10.1080/08957959.2016.1269900

Cited by 12 publications

(9 citation statements)

References 28 publications

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“…The samples were probed using an angle-dispersive X-ray powder diffraction technique at the synchrotron beam lines AR-NE1A at the Photon Factory or BL10XU at SPring-8. Experimental assemblies for synchrotron X-ray measurements have been described elsewhere 24,25 . A monochromatic incident X-ray beam was used in both synchrotron beam lines.…”

Section: Methodsmentioning

confidence: 99%

Fate of subducted argon in the deep mantle

Ono

2020

Sci Rep

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The physical properties of argon (Ar) are investigated to 382 GPa and 3000 K using diamond anvil cell experiments and first-principles molecular dynamics. The estimated density of Ar is smaller that of the preliminary reference earth model (pReM) mantle, which indicates that the density crossover does not occur at the bottom of the lower mantle. A large volume dependence of the thermal pressure of Ar is revealed at pressures higher than 200 GPa, and a significant temperature dependence of the calculated effective Grüneisen parameters is confirmed at high pressures. A melting temperature of Ar is estimated from the calculation data and a significant pressure dependence is confirmed. If the pressuretemperature path of the subducted slab is lower than the critical condition, ~750 K and ~7.5 GPa, solid Ar can be carried down into the deep mantle. Melting of solid Ar in the upwelling mantle plume occurs at the bottom of the transition zone. Thus, solid Ar plays an important role in Ar recycling in the Earth's interior. It is known that noble gases are key tracers to understand the evolution of the Earth because of their inert nature and isotope variations. However, the mechanism of the recycling of noble gases in the deep mantle is still an open question. As the noble gases are the inert, any host phases of noble gases are not expected to transport into the deep mantle. Therefore, the role of grain boundaries in the storage of noble gases has been discussed 1,2. Recently, an experimental study demonstrated high solubility of noble gases in amphibole 3. Amphibole is commonly observed in the altered oceanic crust, with a significant amount of noble gases measured in natural rock samples from Ocean Drilling Program sites 4. Amphibole has a mineralogical A-site, which is an energetically favourable position for noble gases. Lattice structures of some hydrous minerals, such as serpentine and chlorite, are similar to the A-site in amphibole. This indicates that these hydrous minerals are candidates for the host phases of noble gases. In fact, Kendrick et al. 5 measured the concentration of noble gas isotopes in metamorphic rocks and found that the signature of noble gas in serpentinites reflects that of sea water. As the breakdown of serpentine finishes at the upper part of the upper mantle (~200 km depth), it is difficult to transport to great depths in the deep mantle. Argon is a noble gas and has three isotopes, 36 Ar, 38 Ar and 40 Ar. Holland and Ballentine 6 proposed that Ar from the mantle is identical to the seawater component using isotope analysis. This indicates that seawater recycling dominates the behaviour of Ar in the mantle. In contrast, the systematic analysis of isotopes of noble gases indicates that ocean island basalt has a primordial signature that is different from the atmospheric component 7. The recycling of Ar between the Earth's surface and the deep mantle has been discussed using the isotope data of noble gases. However, it is difficult to understand the mechanism of recycling of Ar because of a la...

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Section: Methodsmentioning

confidence: 99%

Fate of subducted argon in the deep mantle

Ono

2020

Sci Rep

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“…The octahedral assembly was compressed to a pressure of 16 and 20 GPa and, at pressure, heated to a chosen temperature in the range of 1800-2000 °C and held for 30 min. Pressure was calibrated at room temperature using the semiconductor to metal transition of GaP at 22 GPa 33 . Sample temperatures were estimated using power-temperature relations calibrated in a separate run using a W5%Re/W26%Re thermocouple (C-type).…”

Section: Methodsmentioning

confidence: 99%

Discovery of Ternary Silicon Titanium Nitride with Spinel-Type Structure

Bhat

Lale

Bernard

et al. 2020

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Here we report on the discovery of a ternary silicon titanium nitride with the general composition (Si 1−x ,ti x) 3 n 4 with x = 0 < x < 1 and spinel-type crystal structure. The novel nitride is formed from an amorphous silicon titanium nitride (Sitin) precursor under high-pressure/high-temperature conditions in a large volume high-pressure device. Under the conditions of 15-20 GPa and 1800-2000 °C, spineltype γ-Si 3 n 4 and rock salt-type c-TiN are formed. In addition, crystals of the discovered nano-sized ternary phase (Si 1−x ,ti x) 3 n 4 embedded in γ-Si 3 n 4 are identified. The ternary compound is formed due to kinetically-controlled synthesis conditions and is analyzed to exhibit the spinel-type structure with ca. 8 atom% of Ti. The Ti atoms occur in both Ti 3+ and ti 4+ oxidation states and are located on the Si sites. the ternary nano-crystals have to be described as (Si,ti) 3 n 4 with n-vacancies resulting in the general composition (Si 4+ 1−x ti 4+ x-δ ti 3+ δ) 3 n 4-δ .

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“…The onset of oS 24 GaP instability upon decompression occurs within its calculated stability field. Furthermore, the SC16 phase was not observed experimentally, even upon heating . Inconsistencies among different experiments and with calculations are very common in high-pressure semiconductor studies. − While some differences between predictions and experiments ought to be expected, the combination of rich phase diagrams with narrow stability ranges for phases such as SC16, experimental limitations (chiefly nonhydrostatic conditions and low resolution, here dramatically improved), and most importantly the kinetic hindrance of the transition between all these phases, can explain seemingly inconsistent observations.…”

Section: Resultsmentioning

confidence: 99%

“…Diffraction analysis suggests that oS 8 GaP is a long-range, site-disordered structure, , whereas extended X-ray absorption fine structure (EXAFS) data recorded at the gallium K -edge ( E = 10.367 keV) show that Cmcm GaP is a short-range ordered structure with 6 Ga–P bonds and no Ga–Ga bonds at 39 GPa . A recent study suggests a nearly isobaric boundary at ∼22 GPa between ZB and oS 8 phases up to ∼800 K . In spite of the wealth of experimental and theoretical investigations of the ZB → Cmcm transition, it remains unclear if site-disordered arrangements exist in the Cmcm GaP phase, which is of crucial importance to understand the nature of phase transitions in this class of octet semiconductors.…”

Section: Introductionmentioning

confidence: 99%

Phosphorus Dimerization in Gallium Phosphide at High Pressure

et al. 2018

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Using combined experimental and computational approaches, we show that at 43 GPa and 1300 K gallium phosphide adopts the super- Cmcm structure, here indicated with its Pearson notation oS24. First-principles enthalpy calculations demonstrate that this structure is more thermodynamically stable above ∼20 GPa than previously proposed polymorphs. In contrast to other polymorphs, the oS24 phase shows a strong bonding differentiation and distorted fivefold coordination geometries of both P atoms. The shortest bond of the phase is a single covalent P-P bond measuring 2.171(11) Å at synthesis pressure. Phosphorus dimerization in GaP sheds light on the nature of the super- Cmcm phase and provides critical new insights into the high-pressure polymorphism of octet semiconductors. Bond directionality and anisotropy explain the relatively low symmetry of this high-pressure phase.

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Determination of the phase boundary of GaP using in situ high pressure and high-temperature X-ray diffraction

Cited by 12 publications

References 28 publications

Fate of subducted argon in the deep mantle

Fate of subducted argon in the deep mantle

Discovery of Ternary Silicon Titanium Nitride with Spinel-Type Structure

Phosphorus Dimerization in Gallium Phosphide at High Pressure

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