Structural characterization of SiO2-CsAlO2 and SiO2-RbAlO2 glasses

Glasses along the SiO2-CsAlO2 and SiO2-RbAlO2 joins were prepared by a sol-gel method and studied using Si-29 and Al-27 nuclear magnetic resonance and by infrared and Raman spectroscopy. The Si-29 and Al-27 chemical shifts follow the same trend with composition as found in previous studies, due to the formation of Q(4)(1Al) and Q(4)(2Al) species in the glass, consistent with Raman spectroscopy. The Raman spectra indicate a larger proportion of 3-membered (Si, Al)-containing rings than is present in other alkali aluminosilicate glasses with similar silica content. This effect occurs because the large alkali cations (Cs+, Rb+) require the formation of large cages in the glass structure, which in return requires the simultaneous formation of additional small rings. (C) 1998 Elsevier Science B.V. All rights reserved.