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 res onance and by infrared and Raman spectroscopy. The Si-29 and Al-27 che mical shifts follow the same trend with composition as found in previo us studies, due to the formation of Q(4)(1Al) and Q(4)(2Al) species in the glass, consistent with Raman spectroscopy. The Raman spectra indi cate 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 ring s. (C) 1998 Elsevier Science B.V. All rights reserved.