CONNECTION BETWEEN FICTIVE TEMPERATURE AND STRUCTURAL DEFECTS RESPONSIBLE FOR THE RELAXATIONAL PROCESSES IN OXIDE GLASSES

Raman spectra have been investigated in the 3-1500 cm(-1) range in two sodium oxide phosphosilicate glasses with differing fictive temperatu res, T-f. The temperature dependence of the spectra has been measured from lower temperatures to the glass transition temperature, T-g. Up t o T-g the Bose-factor rescaled spectra coincide, but a dynamical quasi elastic contribution depending on T-f, was observed in a large range o f temperature. Relaxational processes related to a structural reorderi ng are observed near T-g. A connection between T-f and medium range or der deduced from inelastic light scattering in this frequency range is emphasized. This study point out that the quasielastic scattered inte nsity originates from thermally activated structural entities related to the disorder. (C) 1998 Elsevier Science B.V. All rights reserved.