Site connectivities in silver borophosphate glasses: new results from 11B{31P} and 31P{11B} rotational echo double resonance NMR spectroscopy

The effect of composition on the structure of sodium borophosphate glasses

“…The band at À18/À19 ppm is probably the result of contributions from different types of phos- phorus tetrahedra; this is suggested by the consistent width of the band at À18/À19 ppm ($16 ppm) and its progressive increase with B 2 O 3 content. Although the peak at À18/À19 ppm is an evolution of the most negatively shifted peak in the lower boron-content glasses, given the composition and shift, in agreement with the chemical shift values reported in the literature [13,24], the resonance at around À18/À19 ppm arises from the contribution of P 3 2B and P 3 1B groups, i.e. Q 3 phosphate tetrahedra with one terminal oxygen, one or two oxygens linked to boron and the remaining oxygen connected to phosphorus.…”

“…In a borate network, the addition of a modifier oxide has the opposite effect, i.e. it increases the degree of polymerization: given the acidic Lewis character of B 2 O 3 , the boron coordination changes from trigonal to tetrahedral, and the basic units change from BO 3 to BO 4 [12,13]. We note that pure phosphate and borate networks can be classified depending on the way the tetrahedra are linked to each other.…”

“…Polyhedra around phosphorus and boron are considered separately; phosphate and borate units are distinguished by the number of phosphate or borate groups that are connected to them. The corresponding 31 P and 11 B chemical shift ranges have been assigned on the basis of previous 11 B-31 P double-resonance NMR studies on borophosphate glasses which give detailed information on the boron-phosphorus interaction within the network [13,24].…”

Short and Medium Range Order in Ion-Conducting Glasses Studied by Modern Solid State NMR Techniques

“…Similar preferences for heteroatomic linkages were detected by comprehensive spectroscopic studies of the sodium and silver borophosphate glass system along other composition lines [27,[79][80][81][82], in sodium aluminophosphate glasses [83] and in sodium aluminoborate glasses [84][85][86]. In contrast, preferences for homo-atomic connectivities were detected by dipolar NMR spectroscopic methods in borosilicate [87] 3 , and TeO 2 can be incorporated into glassy NaPO 3 , over wide composition ranges, producing strong effects on their physical properties.…”

“…Spectral assignments are made in terms of the local P (n) mB and B (n) mP units, where n is the number of bridging oxygen atoms and m is the number of heteroatomic bridges for each network former type. These assignments are based on appropriate mass and charge balance constraints [78] and are partially assisted by 31 P{ 11 B} and 11 B{ 31 P} REDOR experiments [27,[79][80][81]. The detailed phosphate and borate speciations as extracted from these spectra, are summarized in Fig.…”