The vibrational spectra of B2O3-GeO2 glasses

Infrared and Raman spectra were measured for a series of glass compositions in the binary B2O3-GeO2 system at room and elevated temperatures. No coordination changes were detected from spectral analysis for either boron or germanium with concentration or temperature changes. Interpretation of the vibrational spectra indicated that both boroxol rings and BO3-triangular units were present as the basic units in glasses with higher B2O3 concentrations. Only BO3-triangular units were detected as the basic units in glasses with lower B2O3 concentrations. Raman spectra of glasses measured at higher temperatures (>Tg) indicated that their boroxol ring concentrations decreased as a function of temperature. The enthalpy for ring rupture in 35GeO2–65B2O3 glass was 7.7 kcal/mol. Also, spectral analysis indicated that the boroxol ring concentrations of these glasses at room temperature were dependent upon their previous heat treatments.