The Structure of Borophosphosilicate Pure Network Former Glasses Studied by Multinuclear NMR Spectroscopy

Abstract

New mixed network glasses along the composition line xB2O3–(30 – x)­P2O5–70SiO2 have been prepared and characterized in terms of their chemical composition, viscosity, and characteristic temperatures. The physical properties have been correlated with structural information, obtained from Raman spectroscopy and advanced 11B, 29Si, and 31P single and double resonance solid state NMR studies. Both the macroscopic and structural properties show nonlinear changes as a function of composition, with maximal values of the viscometric glass transition temperature near 12–13 mol % B2O3. The structure of phosphorus-rich glasses is dominated by tetrahedral B(4) units linked to three to four phosphorus species and multiple phosphorus environments, including P(3) (branching phosphate) groups linked to silicon, and P(4) units forming B–O–P linkages as in boron phosphate, BPO4 (superscripts denote the number of bridging oxygen species). In the boron-rich region, the phosphorus species are exclusively present as P(4) groups and the boron atoms present in excess of a B/P ratio of unity are present in the form of three-coordinated B(3) units forming both B–O–B and B–O–Si linkages. While these results document a strong mutual affinity of the boron oxide and phosphorus oxide components, the species concentrations and numbers of B–O–P linkages fall consistently below those numbers expected from a clustering scenario maximizing the number of such connectivities, indicating the absence of macroscopic phase separation. Important differences relative to the previously studied system xAl2O3–(30 – x)­P2O5–70SiO2 are discussed.

Solid State NMR: A Powerful Tool for the Characterization of Borophosphate Glasses

“…Finally, we believe that this overall methodology will then be applied to much more complex systems, especially when a borophosphate network is accompanied by another GFO like SiO 2 [71] or Al in four-fold coordination. As shown in Figure 10, the extent of mixing in a modifier free Al 2 O 3 -B 2 O 3 -P 2 O 5 glass can be efficiently analyzed with 11 B, 27 Al and 31 P 1D NMR spectra and the 11 B( 31 P) 2D map.…”

Topological Engineering of Photoluminescence Properties of Bismuth‐ or Erbium‐Doped Phosphosilicate Glass of Arbitrary P2O5 to SiO2 Ratio

“…[11,18] By adjusting the crosslinking degree of phosphate chains, it has been demonstrated that the precipitation of metallic nanoparticles in the phosphate glasses can be tailored through network topology. Moreover, for glasses consisting of two or three different kinds of glass formers, the glass networks remain virtually dominated by one type of topological structures, for example, formation of certain types of B-O-P and B-O-Si linkages of medium range scale (5-20 Å) [20] Hence, the mixed-former-glasses still suffer from limited site-to-site variations for the dopants. Zhou et al found that the aggregation state of dopants (e.g., bismuth or rare earth ions) can be finely tuned via the topological engineering, such that the much enhanced emissions of the dopants can be realized.…”

“…[15] However, it still remains fundamentally challenging to reliably arrange the active dopants settling in as many different sites in glass as possible, especially those sites that differ considerably in chemical environments. Moreover, for glasses consisting of two or three different kinds of glass formers, the glass networks remain virtually dominated by one type of topological structures, for example, formation of certain types of B-O-P and B-O-Si linkages of medium range scale (5-20 Å) [20] Hence, the mixed-former-glasses still suffer from limited site-to-site variations for the dopants. [21,22] In contrast to the conventional glass-making method, that is, melting the target compositions simultaneously and altogether in a single crucible followed by rapid quenching, a new inhouse developed approach is described in this article for manufacturing glasses of arbitrary mixing of very different types of glass formers.…”

Insertion of Al2O3 in Zinc Metaphosphate Glasses: New Insights from 1D/2D Solid State NMR

“…The M 2 values (Van Vleck second moment) can then be used to determine the number of P atoms surrounding the Al atoms. More information about this sequence (and all the REDOR derived NMR techniques) used to determine the nature of P­(OX) a and X­(OP) b structural groups (X = Al, B) for many alumino- and boro-phosphate based systems can be found in refs and − . In our experiments, the set of data was acquired at ν rot = 12.5 kHz with 16 and 10 μs π pulse lengths for 27 Al and 31 P, 256 transients, and a rd of 2 s.…”