Raman study of Bi2O3-GeO2-SiO2 glasses

Raman spectra have been obtained for 2Bi 2 O 3 -3[(GeO 2 ) x -(SiO 2 ) 1-y ][2-3 composition) and 6Bi 2 O 3 -[(GeO 2 ) x -(SiO 2 ) 1-x ] (6-1 composition) glasses at different Ge/Si nominal ratios. In both compositions, the vibrational structure at low frequencies is nearly independent of x. At higher frequencies, typical vibrations are found which may be attributed to Ge-O and Si-O bonds in GeO 4 and SiO 4 tetrahedral units, respectively, as observed in mixed crystals with the same stoichiometric formula.