Probing alkali coordination environments in alkali borate glasses by multinuclear magnetic resonance

Structure–property correlations in lead borate and borosilicate glasses doped with aluminum oxide

“…They are also consistent with boron speciation in other metal-oxide borate glasses such as ZnO-B 2 O 3 [64], CdO-B 2 O 3 [65] and SnO-B 2 O 3 [19] which have maximum N 4 values at 50 mol% metal oxide. Note that this contrasts sharply with the well-known case of alkali borates, where non-bridging oxygens begin to form much earlier, resulting in a maximum N 4 at about 35 mol% M 2 O [48,62,66].…”

“…The sharpness and symmetry of the [4] B peak are due to a very small quadrupolar coupling constant for the high-symmetry pseudo-tetrahedral site. While multiple distinct [4] B signals are often observed as asymmetric peaks for alkali borate and borosilicate glasses [61,62], the fairly broad linewidths found here (FWHM = 2 ppm) suggest significant disorder and/or a wide range of unresolved tetrahedral sites in all glasses.…”

Effects of cation field strength on the structure of aluminoborosilicate glasses: High-resolution 11B, 27Al and 23Na MAS NMR

“…Apparently the mechanism for formation of NBO + [3] B (reaction (3)) is predominant when high cation field strength modifiers are present, especially in glass compositions that are relatively rich in silica, where dilution of B and Al by Si in the network lowers the probability of such highly charged bridging oxygens. However, it has been suggested that the stabilization of [4] B-O- [4] B linkages by small alkali cations (e.g., Li + ) in high-alkali binary borate glasses may explain their higher N 4 values relative to those with large alkali cations (e.g., Cs + ) [36,51,68]. Steric hindrance for the latter makes charge compensation of such linkages especially difficult [69], perhaps promoting instead the formation of NBO.…”

Structural investigation of bismuth borate glasses and crystalline phases

“…The occurrence of wide range of unresolved tetrahedral sites is often observed as an asymmetric [BO 4 ] peak in the NMR spectra of alkali borate and borosilicate glasses [51,52]. Four main types of triangularly coordinated boron species can be found for various loadings of a network modifier in borate glasses: T 3 groups possess three oxygens bridging to other network formers, T 2 groups possess two bridging oxygens and one non-bridging oxygen, T 1 have one bridging and two non-bridging oxygens, and T 0 have three non-bridging oxygens.…”