¹¹ B and ²⁷ Al Nuclear Quadrupole Interactions in SiO ₂ ‐B ₂ O ₃ ‐Al ₂ O ₃ ‐R ₂ O Glass Systems

Abstract

Quadrupole interactions of 11 B and 27 Al in SiO 2 ‐B 2 O 3 ‐Al 2 O 3 ‐R 2 O glass systems were investigated to determine the structure of these glasses, which should be amenable to chemical strengthening. The ratio of BO 4 units to BO 3 units approached unity as the R 2 O/Al 2 O 3 ratio for compounds having fixed B 2 O 3 contents approached unity. Nuclear quadrupole coupling constants ( e 2 Qq/h =2.73 to 2.93 MHz) were measured for the NMR spectra of 11 B triangles. The line shapes of 27 Al spectra varied with chemical composition, but a few glasses exhibited 27 Al line shapes similar to those of the AlO 4 triclusters in SiO 2 ‐Al 2 O 3 ‐Na 2 O glasses. Compositional trends in the formation of BO 4 and AlO 4 were deduced from the NMR spectra.