In order to point out the influence of thermal history (fictive temperature)and OH content on the elastic properties of silica glass, we have performedhigh resolution in situ Brillouin spectra of SiO2 glass from room temperatureto the supercooled liquid at 1773K across the glass transition. The well knownanomalous increase of elastic modulus in the glassy state and in thesupercooled liquid regime is observed. No change of slope in the elastic moduliof silica appears as a characteristic of glass transition, on the contrary towhat happens in various other glasses. We show that thermal history has a weakeffect on elastic moduli in the glass transition regime for silica glass. Theeffect of water content in silica glass is more efficient than the fictivetemperature effect and gives larger changes in the amplitude of elastic modulusfor the same thermal dependence. A singular decrease above 1223K is alsoobserved in the shear moduli for hydrated samples. Different models explainingelastic properties temperature dependence in relationship with frozen-indensity fluctuations or with the structure are discussed.
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