Determinations of structure and bonding in vitreous B2O3 by means of B10, B11, and O17 NMR

Abstract

B10, B11, and O17NMR were used to study B2O3 glass. B10NMR was employed to determine the most probable values and the Gaussian widths (σ) of the distributions of the quadrupole coupling constant (Q cc) and the asymmetry parameter (η). The resulting values are Q 0 cc=5.51 MHz, σ Q cc=0.21 MHz, η0=0.12, and ση=0.043. These values are consistent with results using B11NMR. The O17NMR spectra are obtained and analyzed using two sites: site 1 is characterized by Q 0 cc=4.69 MHz, σ Q cc=0.10 MHz, η0=0.58; site 2 is characterized by Q 0 cc=5.75 MHz, η0=0.4, and ση=0.2. Only small distributions are present for site 1 and for Q cc of site 2. A Townes–Daily calculation was employed, using the boroxol ring model of B2O3 glass, to determine the charge distributions and the B–O–B angle outside the boroxol rings. The results are consistent with a structure composed of randomly oriented boroxol rings.