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Titolo:
PHONONS AND RELAXATIONS IN OXIDE AND POLYMERIC GLASSES
Autore:
PELOUS J; PRAT JL; SCHEYER Y; LEVELUT C; TERKI F;
Indirizzi:
UNIV MONTPELLIER 2,LAB VERRES,CASE COURRIER 069,PL EUGENE BATAILLON F-34095 MONTPELLIER 05 FRANCE
Titolo Testata:
Philosophical magazine. B. Physics of condensed matter.Statistical mechanics, electronic, optical and magnetic
fascicolo: 2, volume: 77, anno: 1998,
pagine: 633 - 643
SICI:
1364-2812(1998)77:2<633:PARIOA>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
MEDIUM-RANGE ORDER; LOW-FREQUENCY DYNAMICS; RAMAN-SCATTERING; VITREOUS SILICA;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Science Citation Index Expanded
Science Citation Index Expanded
Science Citation Index Expanded
Citazioni:
19
Recensione:
Indirizzi per estratti:
Citazione:
J. Pelous et al., "PHONONS AND RELAXATIONS IN OXIDE AND POLYMERIC GLASSES", Philosophical magazine. B. Physics of condensed matter.Statistical mechanics, electronic, optical and magnetic, 77(2), 1998, pp. 633-643

Abstract

We present the results of inelastic light scattering measurements (Brillouin and low-frequency Raman scattering) and neutron scattering in two oxide glasses (one phosphosilicate and one heavy-metal oxide) and in polyurethane samples in which the number of cross-links has been varied. These measurements have been performed across the glass transition in solid and undercooled liquid phases. The results showed vibrational and relaxational contributions arising in the so-called boson peakand in the quasielastic contributions respectively. The softening of the vibrational contribution with increasing temperature must be takeninto account in order to extract the relaxational contribution. The correlations between the position of the boson peak measured by Raman or neutron scattering and the hypersound velocity measured by Brillouinscattering on the one hand and between the quasielastic intensity andthe hypersonic attenuation on the other hand are seen in the oxide glasses. In polyurethane the relaxation time deduced from Brillouin datacompares well with that deduced from neutron measurements; it appearsdifferent from that associated with the a relaxation near T-g. Moreover, the density of excitations extracted from the dynamic structure factor demonstrates a conversion of high-frequency modes to low-frequency modes when the temperature increases. Our results suggest that the anharmonicity must be taken into account to explain the low-energy excitations in glasses.

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Documento generato il 30/11/20 alle ore 09:18:57