Inelastic light scattering in B2O3 glasses with different thermal histories

This contribution presents a systematic light scattering study of a series of boron oxide glasses which are characterized by different thermal histori es. The thermal treatment was obtained by annealing the samples close to th e glass transition temperature for times of several hours. Both low-frequen cy (0.1-30 cm(-1)) and high-frequency (5- 1600 cm(-1)) spectra were monitor ed by using a tandem Fabry-Perot interferometer and a Raman spectrometer, r espectively. The low-frequency spectra include quasielastic contributions a nd the boson peak. It was found that different thermal histories lead to pr onounced changes in the low-frequency spectrum. The position of the boson p eak shifts to higher frequencies and the magnitude of the quasielastic cont ribution decreases as a function of annealing time. Both quantities correla te linearly with the density of the samples (rho=1.804-1.866 g/cm(3)). On t he other hand, the high-frequency modes do not show discernible changes. In particular, no alteration of the modes which correspond to the boroxol rin g is found, indicating that the fraction of boroxol rings is constant withi n 2% accuracy. Taking the boson peak as a manifestation of medium-range ord er, we conclude that annealing the glass influences the intermediate-range order rather than the short-range order. (C) 2000 American Institute of Phy sics. [S0021-9606(00)50734-X].