Accueil >
Production scientifique
(127) Production(s) de HEHLEN B.
|
|
Polarized hyper-Raman scattering study of the silent F2u mode in PbMg1/3Nb2/3O3 
Auteur(s): Al-Zein A., Hehlen B., Rouquette Jérôme, Hlinka Jirka
(Article) Publié:
Physical Review B, vol. 78 p.134113 (2008)
Ref HAL: hal-00338570_v1
DOI: 10.1103/PhysRevB.78.134113
WoS: 000260574200043
Exporter : BibTex | endNote
15 Citations
Résumé: A single crystal of the relaxor PbMg1/3Nb2/3O3 is studied by hyper-Raman scattering. The relative scattering intensities obtained for the band near 250 cm−1 in various polarization geometries are fully compatible with hyper-Raman spectroscopy tensor of the F2u zone-center vibrational mode of prototype Pm3¯m (Oh 1 ) cubic perovskite structure. The mode was investigated between room temperature and 775 K, thus covering the range around the Burns temperature Td and the crossover temperature T(. At variance with recent anticipations, no softening was observed.
|
|
|
|
The vibrational excitations of glasses in the boson-peak region: application to borates
Auteur(s): Vacher R., Ruffle B., Hehlen B., Guimbretiere Guillaume, Simon Guilhem, Courtens E.
(Article) Publié:
European Journal Of Glass Science And Technology: Part B - Physics And Chemistry Of Glasses, vol. 49 p.19-25 (2008)
Ref HAL: hal-00512610_v1
Exporter : BibTex | endNote
Résumé: There exists a special interest in investigating acoustical and optical vibrations of glasses in the one THz frequency region. The main experimental tools that are used to this effect are briefly discussed. The current understanding of the boson-peak vibrations and of their resonance with acoustic branches are explained. Specific new results on the origin of the boson peak and on the end of acoustic branches are presented for borates.
|
|
|
|
Nature of the hyper-Raman active vibrations of lithium borate glasses
Auteur(s): Simon Guilhem, Hehlen B., Vacher R., Courtens E.
(Article) Publié:
Journal Of Physics: Condensed Matter, vol. 20 p.155103 (2008)
Ref HAL: hal-00526787_v1
DOI: 10.1088/0953-8984/20/15/155103
WoS: 000254329200005
Exporter : BibTex | endNote
14 Citations
Résumé: Hyper-Raman spectra of two lithium borate glasses, 4B(2)O(3): Li2O and 2B(2)O(3): Li2O, are compared to those of pure boron oxide glass, upsilon-B2O3. A mode analysis is performed using a structural model based on the symmetry of the elementary structural units (ESUs) constituting the glasses. Most spectral components arise from internal vibrations of BO3 triangles, B3O3 boroxol rings, and BO4 tetrahedra. In particular, a mode associated with stretching motions of BO4 units can be assigned to a vibration of F-2 symmetry in the T-d tetrahedral point group. The hyper-Raman scattering intensity of its transverse optic component appears to be proportional to the number of BO4 units in the glass. The boson peak observed in hyper-Raman scattering arises from external modes of rigid ESUs which correspond to librational motions coupled to their translations. The scattering strength of these modes strongly decreases with increasing Li concentration. In pure upsilon-B2O3, external modes of boroxols presumably dominate this scattering. The decrease in the boroxol concentration in lithium borate glasses correlates with the apparent hardening of the boson peak.
Commentaires: 0953-8984
|
 |
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)
|
|
Evidence by XAS of the Zr shift towards the centrosymmetric position at high pressure in PbZr 0.52 Ti 0.48 0 3
Auteur(s): Al-Zein A., Rouquette J., Fraysse G., Papet P., Haines J., Aquilanti G., Hehlen B., Levelut C.
Conference: 5 th European workshop on piezoelectric materials (Montpellier, France, FR, 2008-08-16)
|
|
Structure and Vibration Investigation in Materials
Auteur(s): Hehlen B.
(Séminaires)
Schott (Mainz, Germany, FR), 2008-03-07 |
|
Polarized hyper-Raman scattering of the silent F 2u mode in PbMg 1/3 Nb 2/3 O 3
Auteur(s): Al-Zein A., Hlinka J., Rouquette J., Hehlen B.
(Affiches/Poster)
5 th European workshop on piezoelectric materials (Montpellier, France, FR), 2008-08-16 |
