IR and Raman study of calcium aluminosilicate glasses of the composition xCaO ∙ xAI2O3 ∙ (100 - 2x)SiO2

Abstract

Vibrational spectra are measured for calcium aluminosilicate glasses with the composition (in mol%) xCaO ∙ xAI2O3 ∙ (100 - 2x)SiO2. 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 60 1 ∙ 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 0.49 1 ∙ mol-1 ∙ cm-1 with increasing x from 15 to 32. Systematic changes in the Raman and IR reflectance spectra reflect the substitution of Al3+ for Si4+ and a corresponding increase of Ca2+ 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.