Article

# Silica under hydrostatic pressure: A non continuous medium behavior

(Impact Factor: 1.77). 10/2009; 4340(48-49). DOI: 10.1016/j.jnoncrysol.2009.08.031

ABSTRACT

a b s t r a c t The homogeneous/inhomogeneous structure of glasses is still a debated question. Hydrostatic high pres-sure experiments allow us to determine if a glass behaves as an elastic continuous random network or if a nanometer scale heterogeneity has to be taken into account. In order to get information on the homoge-neous/inhomogeneous structure of glasses, in situ high pressure Raman experiments are performed on silica in the elastic domain up to 4.7 GPa. A strong decrease of the Boson peak intensity is observed between 1 bar and 3 GPa. We show that this decrease does not correspond quantitatively to the effect of pressure on a homogeneous elastic medium. From the interpretation of the narrowing of the main Raman band width under pressure as a narrowing of the h inter-tetrahedral Si–O–Si angle distribution it is shown that the decrease of the Boson peak intensity is correlated to the decrease of the intrinsic inho-mogeneity of the silica glass. These results confirm the occurrence of an intrinsic inhomogeneity at a nanometer scale even in a single component glass like SiO 2 which is very important for the interpretation of the optical or mechanical properties of the glasses.

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Available from: Daniel Neuville, Oct 06, 2015
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ABSTRACT: The evolution of the boson peak with densification at medium densification rates (up to 2.3%) in silicate glasses was followed through heat capacity measurements and low frequency Raman scattering. It is shown that the decrease of the boson peak induced by densification does not conform to that expected from a continuous medium; rather it follows a two step behaviour. The comparison of the heat capacity data with the Raman data shows that the light-vibration coupling coefficient is almost unaffected in this densification regime. These results are discussed in relation to the inhomogeneity of the glass elastic network at the nanometre scale.
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##### Article: The boson peak of silicate glasses: The role of Si-O, Al-O, and Si-N bonds
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