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(116) Production(s) de LEVELUT C.
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Collapsed silicalite at high pressure: a novel form of topologically ordered amorphous structure
Auteur(s): Haines Julien, Levelut C., Isambert Aude, Hébert Philippe, Kohara Shinji, Keen David, Hammouda Tahar, Andrault Denis
Conference: 47th EHPRG (European High Pressure Group (, FR, 2009-09-06)
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An in situ x-ray absorption spectroscopy study of the solubility of cristobalite-type
Si$_{0.8}$Ge$_{0.2}$O$_2$ and aqueous spaciation of Ge in hydrothermal conditions
Auteur(s): Ranieri Vincent, Haines Julien, Cambon Olivier, Levelut C., Le Parc R., Cambon Martine, Hazemann Jean-louis
(Affiches/Poster)
47th EHPRG (European High Pressure Group (paris, FR), 2009-09-10 |
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Probing the giant piezoelectric effect at the atomic scale in PbZn$_{1/3}$Nb$_{2/3}$O$_3$
Auteur(s): Rouquette Jérôme, Al-Zein A., Fraysse Guillaume, Haines Julien, Papet Philippe, Levelut C., Dammak Hichem, Mathon Olivier
(Affiches/Poster)
25th European Critsllographic Meeting (Istambul, TR), 2009-08-18 |
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Etude par diffraction X des effets de dépressurisation locale lors de l'amorphisation des zéolites sous pression
Auteur(s): Levelut C., Rouquette Jérôme, Al-Zein A., Fraysse Guillaume, Haines Julien, Papet Philippe, Aquilanti Giuliana, Joly Yves
Conference: 25th European Critsllographic Meeting, Istambul (Istambul, TR, 2009-08-16)
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Initial Structure Memory of Pressure-Induced Changes in the Phase-Change Memory Alloy Ge2Sb2Te5 
Auteur(s): Krbal Milos, Kolobov Alex, Haines Julien, Fons Paul, Levelut C., Le Parc R., Hanfland Michael, Tominaga J., Pradel Annie, Ribes Michel
(Article) Publié:
Physical Review Letters, vol. 103 p.115502 (2009)
Ref HAL: hal-00434398_v1
PMID 19792382
DOI: 10.1103/PhysRevLett.103.115502
WoS: 000269718700031
Exporter : BibTex | endNote
47 Citations
Résumé: We demonstrate that while the metastable face-centered cubic (fcc) phase of Ge2Sb2Te5 becomes amorphous under hydrostatic compression at about 15 GPa, the stable trigonal phase remains crystalline. Upon higher compression, a body-centered cubic phase is obtained in both cases around 30 GPa. Upon decompression, the amorphous phase is retained for the starting fcc phase while the initial structure is recovered for the starting trigonal phase. We argue that the presence of vacancies and associated subsequent large atomic displacements lead to nanoscale phase separation and loss of initial structure memory in the fcc staring phase of Ge2Sb2Te5.
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In situ high pressure and high temperature Raman studies of (1-x)SiO2xGeO2 glasses
Auteur(s): Le Parc R., Ranieri Vincent, Haines Julien, Cambon Martine, Cambon Olivier, Levelut C., Clement S.
(Article) Publié:
Journal Of Physics: Condensed Matter, vol. 21 p.375109 (2009)
Ref HAL: hal-00434405_v1
PMID 21832340
DOI: 10.1088/0953-8984/21/37/375109
WoS: 000269198900011
Exporter : BibTex | endNote
9 Citations
Résumé: The structure of glasses in the binary system SiO2-GeO2 has been studied by Raman spectroscopy. Our results are consistent with mixing of SiO2 and GeO2 tetrahedra. The changes induced by temperature and by pressure on the structure are monitored by in situ measurements on the same mixed glasses. Anomalous temperature dependences are observed not only for SiO2 glass and GeO2 glass but also for mixed glasses. Particular attention is focused on the pressure densification mechanism in mixed glasses. Via the pressure dependence of the width of the main Raman band, we show that the compression mechanism in mixed glasses is intermediate between that of the end members.
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Topologically Ordered Amorphous Silica Obtained from the Collapsed Siliceous Zeolite, Silicalite-1-F: A Step toward Perfect Glasses
Auteur(s): Haines Julien, Levelut C., Isambert Aude, Hébert Philippe, Kohara Shinji, Keen David, Hammouda Tahar, Andrault Denis
(Article) Publié:
Journal Of The American Chemical Society, vol. 131 p.12333-12338 (2009)
Ref HAL: hal-00434413_v1
PMID 19705916
DOI: 10.1021/ja904054v
WoS: 000269379600066
Exporter : BibTex | endNote
76 Citations
Résumé: A dense amorphous form of silica was prepared at high pressure from the highly compressible, siliceous zeolite, silicalite-1-F. Reverse Monte Carlo modeling of total X-ray scattering data shows that the structure of this novel amorphous form of SiO2 recovered under ambient conditions is distinct from vitreous SiO2 and retains the basic framework topology (i.e., chemical bonds) of the starting crystalline zeolite. This material is, however, amorphous over the different length scales probed by Raman and X-ray scattering due to strong geometrical distortions. This is thus an example of new topologically ordered, amorphous material with a different intermediate-range structure, a lower entropy with respect to a standard glass, and distinct physical and mechanical properties, eventually approaching those of an “ordered” or “perfect” glass. The same process in more complex aluminosilicate zeolites will, in addition, lead to an amorphous material which conserves the framework topology and chemical order of the crystal. The large volume collapse in this material may also be of considerable interest for new applications in shock wave absorption.
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