title: Structural heterogeneity and pressure-relaxation in compressed borosilicate glasses by in situ small angle X-ray scattering.
abstract: We report on Brillouin and in situ small angle X-ray scattering (SAXS) analyses of topological heterogeneity in compressed sodium borosilicate glasses. SAXS intensity extrapolated to very low angular regimes, I(q = 0), is related to compressibility. From Brillouin scattering and analyses of the elastic properties of the glass, the Landau-Placzek ratio is determined and taken as a direct reflection of the amplitude of frozen-in density fluctuations. It is demonstrated that with increasing fictive pressure, topological (mid- and long-range) homogeneity of the glass increases significantly. Heating and cooling as well as isothermal scans were performed to follow the evolution of density fluctuations upon pressure recovery. For a sample with a fictive pressure p(f) of 470 MPa, complete recovery to p(f) = 0.1 MPa was observed to occur close to the glass transition temperature. The values of fictive and apparent fictive temperature, respectively, as obtained via the intersection method from plots of I(q = 0) vs. temperature were found in good agreement with previous calorimetric analyses. Isothermal scans suggest that mid- and long-range recovery govern macroscopic density relaxation.
authors.affiliation: Department of Material Science, Glass and Ceramics-WW3, University of Erlangen-Nuremberg, Martensstrasse 5, 91058 Erlangen, Germany.
authors.forename: S
authors.initials: S
authors.lastname: Reibstein
authors.forename: L
authors.initials: L
authors.lastname: Wondraczek
authors.forename: D
authors.initials: D
authors.lastname: de Ligny
authors.forename: Sebastian
authors.initials: S
authors.lastname: Krolikowski
authors.forename: S
authors.initials: S
authors.lastname: Sirotkin
authors.forename: J-P
authors.initials: JP
authors.lastname: Simon
authors.forename: V
authors.initials: V
authors.lastname: Martinez
authors.forename: B
authors.initials: B
authors.lastname: Champagnon