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 histories. The thermal treatment was obtained by annealing the samples close to the glass transition temperature for times of several hours. Both low-frequency (0.1-30 cm(-1)) and high-frequency (5- 1600 cm(-1)) spectra were monitored by using a tandem Fabry-Perot interferometer and a Raman spectrometer, respectively. The low-frequency spectra include quasielastic contributions and the boson peak. It was found that different thermal histories lead to pronounced changes in the low-frequency spectrum. The position of the boson peak shifts to higher frequencies and the magnitude of the quasielastic contribution decreases as a function of annealing time. Both quantities correlate linearly with the density of the samples (rho=1.804-1.866 g/cm(3)). On the other hand, the high-frequency modes do not show discernible changes. In particular, no alteration of the modes which correspond to the boroxol ring is found, indicating that the fraction of boroxol rings is constant within 2% accuracy. Taking the boson peak as a manifestation of medium-range order, we conclude that annealing the glass influences the intermediate-range order rather than the short-range order. (C) 2000 American Institute of Physics. [S0021-9606(00)50734-X].