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(116) Production(s) de LEVELUT C.
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Density and concentration fluctuations in SiO2-GeO2 optical fiber glass investigated by small angle x-ray scattering 
Auteur(s): Le Parc R., Champagnon Bernard, Levelut C., Martinez Valérie, David Laurent, Faivre A., Flammer Ivo, Hazemann Jean-Louis, Simon J.
(Article) Publié:
Journal Of Applied Physics, vol. 103 p.094917 (2008)
Ref HAL: hal-00385046_v1
Exporter : BibTex | endNote
Résumé: Density and concentration fluctuations have been investigated in a 3 mol % GeO2 doped silica glass as a function of the fictive temperature (the temperature at which the structure of the supercooled liquid has been frozen-in to form the glass) by small angle x-ray scattering measurements. The fluctuations increase in a way is quite similar to that observed for pure silica glass as a result of density fluctuation fictive temperature dependence. Fluctuations have also been studied in glasses containing different amounts of GeO2 up to 21 mol % GeO2. The fluctuations are shown to increase very strongly with germanium amount as a result of strong concentration fluctuation increase. This observation is in agreement with already observed excess losses in light scattering measurements.
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Temperature independence of pressure-induced amorphization of the phase-change memory alloy Ge2Sb2Te5
Auteur(s): Krbal Milos, Kolobov Alex, Haines Julien, Annie Pradel, Michel Ribes, Paul Fons, Tominaga J., Levelut C., Le Parc R., Hanfland Michael
(Article) Publié:
Applied Physics Letters, vol. 93 p.031918 (2008)
Ref HAL: hal-00341455_v1
DOI: 10.1063/1.2956409
WoS: 000257968700035
Exporter : BibTex | endNote
29 Citations
Résumé: n the temperature range from room temperature to about 150 °C, the prototypic phase-change material Ge2Sb2Te5 becomes amorphous upon hydrostatic compression. In the studied temperature range, the onset of amorphization is at about 15 GPa and the material completely amorphizes at 25 GPa; these values do not depend on temperature. Upon decompression, the amorphous phase is stable at lower temperatures, yet at higher temperatures (145 °C), the initial fcc phase is recovered upon decompression. A possible mechanism of pressure-induced amorphization and its implications for phase-change memories are discussed.
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Amorphization of faujasite at high pressure: an X-ray diffraction and Raman spectroscopy study
Auteur(s): Isambert Aude, Angot Emmanuel, Hébert Philippe, Haines Julien, Levelut C., Le Parc R., Ohishi Yasuo, Kohara Shinji, Keen David
(Article) Publié:
Journal Of Materials Chemistry, vol. 18 p.5746 - 5752 (2008)
Texte intégral en Openaccess : 
Ref HAL: hal-00341435_v1
DOI: 10.1039/b809774g
WoS: 000261745400005
Exporter : BibTex | endNote
34 Citations
Résumé: In situ X-ray diffraction and Raman spectroscopy measurements of synthetic powdered samples of faujasite 13X were carried out at high pressure using diamond anvil cells. Structural changes are detected, linked to a progressive reduction in crystallinity, before complete amorphization of the material. Three distinct compressibility regions are clearly observed, delimited by two discontinuities in the pressure dependence of the faujasite volume around 2 and 3.5 GPa. The transition from the crystal to the amorphous state is incomplete and partially reversible below pressures of between 8 and 12 GPa, depending on the pressure-transmitting medium used. This partial recovery of the initial structure, at least on a local level, could be related to the presence of hydrated sodium ions in the faujasite framework. In addition, the position of the first sharp diffraction peak in the X-ray diffraction pattern of a fully amorphous sample recovered from 24 GPa is consistent with the presence of 4-membered rings of tetrahedra and the persistence of a significant number of larger rings as compared to a dried amorphous faujasite precursor.
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Probe of the ferroelectric-paraelectric phase transition in the P-T space
Auteur(s): Rouquette J., Al-Zein A., Fraysse G., Papet P., Haines J., Aquilanti G., Levelut C.
Conference: 46 th EHPRG (Valencia, Spain, FR, 2008-09-07)
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Pressure-Induced Phase Transitions in Phase Change Memory Alloy GeTe-Sb 2 Te 3
Auteur(s): Levelut C.
Conference: 46 th EHPRG (Valence, Spain, FR, 2008-09-07)
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Amorphisation sous pression dans des zéolites
Auteur(s): Levelut C., Haines Julien, Angot Emmanuel, Isambert Aude, Hébert Philippe, Cambon Olivier, Maurin D.
(Affiches/Poster)
11ième Journées de la Matière Condensée (Strasbourg, France, FR), 2008-08-26 |
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Local structure study of PbZr 0.52 Ti o.48 O 3 by HP-HT EXAFS at Zr-K edge
Auteur(s): Al-Zein A., Rouquette J., Fraysse G., Papet P., Haines J., Aquilanti G., Hehlen B., Levelut C.
Conference: 6éme Forum des technologies de hautes pressions (Batz s/mer, France, FR, 2008-10-06)
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