Raman Spectroscopy of Heat‐Treated B 2 O 3 ‐SiO 2 Glasses

Raman spectra were measured on B 2 O 3 ‐SiO 2 glasses heat‐treated at different temperatures and for different periods of time. It was found that the intensity ratio of the 810‐ and 475‐cm −1 bands depended on the thermal history and composition of glass. The intensity vs heat‐treatment temperature curve exhibited a maximum in the glass‐transition temperature range. High‐temperature Raman spectra were measured on 0.5B 2 O 3 ‐0.5SiO 2 glass, both with increasing and decreasing temperature, between room temperature and 600°C. Above 300°C with increasing temperature, the intensity of the 810‐cm −1 band decreased, whereas the intensity of the 475‐cm −1 band increased. The changes reversed with decreasing temperature. The reversible change of the intensity of the two bands was interpreted as a reversible formation and decomposition of boroxy rings with temperature. The reaction becomes very sluggish below the glass transition so that the intensity ratio stayed constant below 300°C.