The short range structure of sodium phosphate glasses I. MAS NMR studies

Brow, Richard K.; Kirkpatrick, R. James; Turner, Gary L.

doi:10.1016/0022-3093(90)91043-q

Cited by 259 publications

(208 citation statements)

References 14 publications

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“…In this regard, high spinning frequency Based on analyzed data, ppm. It can be seen from Figure 3 and Table 1 It was confirmed previously that changes in modifier to phosphorus ratio has an effective influence on both structure and properties of glasses [14] [21] [22].…”

Section: P Mas-nmr Spectroscopysupporting

confidence: 72%

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Structural Studies on Ag2O-P2O5 Glasses

El-Damrawi¹,

Hassan²,

Doweidar³

et al. 2017

NJGC

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Silver phosphate glasses of general formula xAg 2 O•(100 − x)P 2 O 5 have been investigated over compositional range from x = 40 to 62.5 mol%. The local structure around phosphorus atom has been studied via 31 P nuclear magnetic resonance. leads to formation of phosphate groups with specific resonance peaks which are mainly related to pyro and orthophosphate species. The rate of change of the chemical shift of the 31 P NMR depends on the bond type, which in turn reflects the extent of double bonding between phosphorus and oxygen atoms. Increasing concentration of Q 0 with increasing Ag 2 O content leads to decreasing quantities of bridging and double bonds. As a consequence, specific symmetric resonance peak of higher intensity and chemical shift (Q 0 ) is a feature of silver rich glasses (orthophosphate). The latter species is therefore proposed to compose of separated membered rings, which cause deshielding of phosphate units. XRD and EDP studies have shown that, amorphous phosphate network is the dominant structure of glasses containing ≤ 55 mol% Ag 2 O. Some ordered and well crystallized phases are formed at higher Ag 2 O concentration. Increasing non-bridging oxygen atoms is shown to have the main effect on crystallization behavior. Orthophosphate composition is the most crystalline one among the other compositions (ultra, meta-and pyrophosphate). Presence of orthophosphate species which typically contains highest concentration from isolated Q 0 units is the main reason for building up crystalline Ag 3 PO 4 phosphate phase.

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Section: P Mas-nmr Spectroscopysupporting

confidence: 72%

“…The movement from a high cross-linked Q 3 structure, to chain-like Q 2 network, to depolymerized Q 1 /Q 0 glasses with increasing Ag 2 O concentration can be monitored by a variety of other spectroscopic probes [22]- [27]. In pure vitreous .…”

Section: Ftir Spectroscopymentioning

confidence: 99%

Structural Studies on Ag2O-P2O5 Glasses

El-Damrawi¹,

Hassan²,

Doweidar³

et al. 2017

NJGC

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“…The 31 P NMR spectra show that the CNP samples consist mainly of Q 2 species, which is to be expected since the glasses contain 50 molar % P 2 O 5 (i.e., it is a metaphosphate, and so should consist of infinite chains or loops of phosphate tetrahedra [37]. The presence of around 5% of the phosphorus sites in these samples exist as Q 1 species indicating some depolymerization, which has been previously observed in calcium metaphosphate glasses [38].…”

Section: Discussionmentioning

confidence: 74%

Doping of a high calcium oxide metaphosphate glass with titanium dioxide

Neel

Chrzanowski

Valappil

et al. 2009

Journal of Non-Crystalline Solids

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a b s t r a c tThis study investigates the effect of doping a high calcium oxide containing metaphosphate glass series (CaO) 40 (Na 2 O) 10 (P 2 O 5 ) 50 with TiO 2 (1, 3, and 5 mol%). TiO 2 incorporation increased the density and glass transition temperature while reduced the degradation rate (5 mol% in particular) by twofold compared with (CaO) 30 system reported previously. This has been confirmed by ion release and the minimal pH changes. TiP 2 O 7 , NaCa(PO 3 ) 3 and CaP 2 O 6 phases were detected for all TiO 2 -containing ceramics. XPS showed that the surface is composed of Ca, P, and Ti. Ti was recognized mainly as TiO 2 , but its total amount was lower than theoretical values. 31 P magic angle spinning (MAS) NMR showed a downfield shift of the 31 P lineshape with increasing TiO 2 , interpreted as an effect of the titanium cation rather than an increase in the phosphate network connectivity. FTIR showed that incorporation of TiO 2 increased the strength of the phosphate chains, and the O/P ratio while introducing more Q 1 units into the structure at the expense of the Q 2 units. There were no differences, however, in surface topography roughness and free energies between these glasses. These results suggested that TiO 2 and CaO were acting synergistically in producing glasses with controllable bulk and structural properties.

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“…For simple binary alkali phosphate glasses all the results obtained so far have documented convincingly the validity of the so-called ''binary'' model, in which the types of phosphate species present in a glass of given composition are only those realized in the two crystalline phases bordering the particular composition considered [6,7]. For ''stoichiometric'' glass compositions corresponding to one of such a crystalline phase only a single type of structural unit is present, which is the one that is featured by this phase.…”

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confidence: 78%