Phase Relationship between 3C‐ and 6H‐Silicon Carbide at High Pressure and High Temperature

Sugiyama, Shin; Togaya, Motohiro

doi:10.1111/j.1151-2916.2001.tb01129.x

Cited by 55 publications

(29 citation statements)

References 12 publications

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“…SiC was present as the cubic 3C modification in the majority of the experiments, while the hexagonal modification occurred only in the experiment with the Mg 50 Si 50 starting composition and crystallized from the melt that did not produce diamond. As is known, preferential crystallization of cubic or hexagonal modifications of silicon carbide is affected by numerous factors, such as temperature, pressure, system composition and impurities [23,24]. The appearance of the 4H-SiC modification in this experiment is possibly related to the system composition, but clarification of this issue lies far beyond the scope of this work.…”

Section: Discussionmentioning

confidence: 75%

HPHT Diamond Crystallization in the Mg-Si-C System: Effect of Mg/Si Composition

et al. 2017

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Crystallization of diamond in the Mg-Si-C system has been studied at 7.5 GPa and 1800 • C with the Mg-Si compositions spanning the range from Mg-C to Si-C end-systems. It is found that as Si content of the system increases from 0 to 2 wt %, the degree of the graphite-to-diamond conversion increases from about 50 to 100% and remains at about this level up to 20 wt % Si. A further increase in Si content of the system leads to a decrease in the graphite-to-diamond conversion degree down to complete termination of diamond synthesis at Si content >50 wt %. Depending on the Si content crystallization of diamond, joint crystallization of diamond and silicon carbide and crystallization of silicon carbide only are found to take place. The cubic growth of diamond, typical of the Mg-C system, transforms to the cube-octahedron upon adding 1 wt % Si and then to the octahedron at a Si content of 2 wt % and higher. The crystallized diamonds are studied by a suite of optical spectroscopy techniques and the major characteristics of their defect-and-impurity structure are revealed. The correlations between the Si content of the Mg-Si-C system and the properties of the produced diamond crystals are established.

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Section: Discussionmentioning

confidence: 75%

HPHT Diamond Crystallization in the Mg-Si-C System: Effect of Mg/Si Composition

et al. 2017

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“…As the structure of SiC may have an impact on material properties, identifying the stable structure at pressure is necessary to improve our understanding of SiC in high-pressure contexts, such as in dynamic applications or in planetary interiors. Several experiments have been performed exclusively on determining stable polytype structures at pressure [14][15][16]. It was found in [14] that the 3C cubic phase was stable at lower temperatures but became more stable with increased pressure, while the 6H phase was preferred at high temperatures (2300-2800 K), at least at pressures of 6.5 GPa and below.…”

Section: High-pressure Crystal Structurementioning

confidence: 99%

High-Pressure, High-Temperature Behavior of Silicon Carbide: A Review

Daviau

Lee

2018

Crystals

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Abstract:The high-pressure behavior of silicon carbide (SiC), a hard, semi-conducting material commonly known for its many polytypic structures and refractory nature, has increasingly become the subject of current research. Through work done both experimentally and computationally, many interesting aspects of high-pressure SiC have been measured and explored. Considerable work has been done to measure the effect of pressure on the vibrational and material properties of SiC. Additionally, the transition from the low-pressure zinc-blende B3 structure to the high-pressure rocksalt B1 structure has been measured by several groups in both the diamond-anvil cell and shock communities and predicted in numerous computational studies. Finally, high-temperature studies have explored the thermal equation of state and thermal expansion of SiC, as well as the high-pressure and high-temperature melting behavior. From high-pressure phase transitions, phonon behavior, and melting characteristics, our increased knowledge of SiC is improving our understanding of its industrial uses, as well as opening up its application to other fields such as the Earth sciences.

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“…Subsequently, shock compression experiments [2] confirmed these findings and found a similar, reversible transformation also for the 6H polytype, at a slightly larger critical pressure. By contrast, the rocksalt phase was never observed in numerous other experiments, even at temperatures up to 2773 K but under lower pressures [3,4]. The only notable exception was a report [5] about traces of a rocksalt phase with lattice parameter of 0.408 nm, attributed to SiC or possibly TiC, observed within the www.pss-b.com intergranular binder material formed during high-energy ball milling of polycrystalline diamond mixed with a Si-T-B alloy powder.…”

Section: Introductionmentioning

confidence: 81%

Phonon instability in nanocrystalline silicon carbide

Cleri

Noda

2006

Physica Status Solidi (b)

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PACS 61.46. Fg, 63.22.+ m In recent experiments by a low-pressure, low-temperature technique, stable nanotubules of rocksalt SiC were synthetized in massive amounts. Ab-initio perturbative density-functional theory calculations in the bulk rocksalt phase provide evidence of drastic phonon softening at a critical pressure of about 2 GPa. To explain the exceptional persistence of the rocksalt structure at ambient conditions we propose that the high pressure induced by interfacial curvature may quench the phonon instability in the nanocrystals down to this minimum threshold, corresponding to the observed nanocrystal size of about 2 nm. Below such pressure the onset of mechanical instability forbids further growth and transformation to ordinary SiC. Nanocrystalline rocksalt SiC is a remarkable example of a material whose unstable, high-pressure phase is stabilized at ambient conditions upon reducing the grain size in the nanometre range.

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Phase Relationship between 3C‐ and 6H‐Silicon Carbide at High Pressure and High Temperature

Cited by 55 publications

References 12 publications

HPHT Diamond Crystallization in the Mg-Si-C System: Effect of Mg/Si Composition

HPHT Diamond Crystallization in the Mg-Si-C System: Effect of Mg/Si Composition

High-Pressure, High-Temperature Behavior of Silicon Carbide: A Review

Phonon instability in nanocrystalline silicon carbide

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