11B-MQMAS and 29Si–{11B} Double-Resonance NMR Studies on the Structure of Binary B2O3–SiO2 Glasses

✍ Scribed by Leo van Wüllen; Georg Schwering

• Publisher: Elsevier Science
• Year: 2002
• Tongue: English
• Weight: 190 KB
• Volume: 21
• Category: Article
• ISSN: 0926-2040
• DOI: 10.1006/snmr.2002.0054

✦ Synopsis

Glasses in the system xB 2 O 3 Á ð1 À xÞSiO 2 ð0:2

x 1:0Þ were studied using 11 B multiple quantum magic angle spinning NMR spectroscopy (MQMAS), 29 Si-f 11 Bg rotational echo adiabatic passage double-resonance and 29 Si-f 11 Bg CP heteronuclear correlation spectroscopy. The results can be quantitatively interpreted in terms of a phase separation of the borosilicate glasses into a virtually SiO 2 -free B 2 O 3 phase and a mixed borosilicate phase. While the MQMAS spectra allowed the site speciation and resolution of at least two different 11 B resonances, attributable to BO 3=2 units consumed in boroxol rings, BO 3=2 units connecting the boroxol rings and BO 3=2 units involved in B-O-Si linkages, the analysis of the double-resonance data further elucidated the structure of the mixed borosilicate phase. The results indicate that only a fraction of 0:48 mol B 2 O 3 can be accommodated per mole SiO 2 , building a mixed borosilicate network.