| Abstract
| - The structural organization of sodium borophosphate glasses with composition (Na2O)0.4[(B2O3)x(P2O5)1-x]0.6(0.0 ≤ x ≤ 1.0) has been investigated by 11B and 31P magic-angle spinnning (MAS) NMR spectroscopy.Spectral deconvolutions and established chemical shift trends yield a detailed quantitative account of thelocal structural units present in these glasses. These units can be described in terms of coordinationpolyhedra P(n)mB and B(n)mP, where n reflects the number of bridging oxygen atoms and mB ≤ n and mP≤ n are the number of connected boron and phosphorus species, respectively. The favorable interactionbetween the two network formers boron oxide and phosphorus oxide results in the dominant formationof B−O−P linkages. Compared to binary sodium phosphate and borate glasses, the extent of networkpolymerization is significantly increased, particularly within the region 0 ≤ x ≤ 0.4, caused by thepreferential formation of four-coordinate boron species linked to phosphorus. Glasses with higher boroncontents also contain three-coordinated BO3/2 units, which appear to interact only weakly with phosphorus.The NMR spectra can be analyzed in terms of the concentration of bridging oxygen atoms per networkformer species, [O], and divided into the quantitative contributions from P−O−P, P−O−B, and B−O−Blinkages. [O] reveals a nonlinear compositional trend showing an excellent correlation with macroscopicproperties such as glass-transition temperatures, densities, and ionic-conductivity parameters.
- The favorable interaction between the two network formers boron oxide and phosphorus oxide sodium borophosphate glasses results in a strong preference of heteroatomic B−O−P linkages, which can be quantified by 31P and 11B magic-angle spinning NMR. The concurrent network densification shows an excellent correlation with the influence of glass composition on glass-transition temperatures and ionic conductivities.
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