BRILLOUIN-SCATTERING IN B2O3-LI2O-LICL GLASS

Brillouin scattering measurement has been carried out in B2O3-Li2O-LiC l glass. The observed Brillouin frequency shift increases with the add ition of a modifier element (both Li2O and LiCl). However, if the rati o of B2O3 to the modifier is a constant, Brillouin frequency shift dec reases with increasing LiCl concentration. In order to obtain addition al information on the local structure, Raman scattering and density me asurements have been performed. Raman spectra have been observed as a distinct peak near 780 cm(-1) which shows the formation of tetrahedral ly coordinated boron. By increasing LiCl concentration, the Raman band near 780 cm(-1) decreases, but the band near 806 cm(-1) increases. Th is illustrates the breathing motion of oxygen in a boroxol ring. This result indicates that LiCl mainly modifies the B2O3 network without fo rming tetrahedrally coordinated boron. By comparing the glass transiti on temperature (T-g) obtained from the temperature dependence of the B rillouin frequency shift with that from the results of differential sc anning calorimetry (DSC) measurement, it is observed that both the val ues of T-g almost agree, The concentration dependence of T-g is discus sed in terms of viscosity.