IR and Raman study of calcium aluminosilicate glasses of the composition xCaO.xAl2O3.(100 - 2x)SiO2

Vibrational spectra are measured for calcium aluminosilicate glasses with the composition (in mol%)xCaO.xAl 2 O 3 .(100 - 2x)SiO 2 . The OH bands show a systematic change with x in both MIR and NIR regions. The strongly asymmetric band at about 3550 cm -1 shifts to lower wave numbers with increasing x. In the same way the OH combination band at about 4500 cm -1 shifts to lower wave numbers. For the 3550 cm -1 band an extinction coefficient of about 601 . mol -1 . cm -1 is suggested for all the samples with x from 15 to 32. For the 4500 cm -1 band the extinction coefficient decreases from 1.0 to 0.491 . mol -1 . cm -1 with increasing x from 15 to 32. Systematic changes in the Raman and IR reflectance spectra reflect the substitution of Al 3+ for Si 4+ and a corresponding increase of Ca 2+ in the network. Thus, the vibrational spectra can be related to a fully polymerized network without or with a small amount of nonbridging oxygens also for glasses with x ≥25.