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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Structure of P2O5-SiO2 Pure Network Former Glasses Studied by Solid State NMR Spectroscopy

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de Oliveira, Jr., Marcos [1] ; Aitken, Bruce [2] ; Eckert, Hellmut [1, 3]
Total Authors: 3
[1] Univ Sao Paulo, Inst Fis Sao Carlos, CP 369, BR-13566590 Sao Carlos, SP - Brazil
[2] Corning Inc, Corning, NY 14831 - USA
[3] Westfalische Wilhelms Univ Munster, Inst Phys Chem, Corrensstr 30, D-48149 Munster - Germany
Total Affiliations: 3
Document type: Journal article
Source: Journal of Physical Chemistry C; v. 122, n. 34, p. 19807-19815, AUG 30 2018.
Web of Science Citations: 2

The structure of binary (SiO2)(100-x)-(P2O5)(x) glasses has been investigated by Raman scattering, Si-29 and P-31 magic angle spinning (MAS) as well as static P-31 NMR spectroscopy. Si-29 chemical shift trends reflect the successive replacement of Si-O-Si by Si-O-P linkages as the compositional parameter x is increased. While P-31 MAS NMR does not resolve separate phosphate species, the static P-31 NMR lineshapes were successfully simulated by considering the effect of uncorrelated distribution functions of the chemical shift tensor components upon the line shape. On the basis of these simulations, which were also found to be consistent with the experimental P-31 MAS NMR spectra, two distinct sites can be resolved: a dominant site characterized by an axially symmetric chemical shift tensor, assigned to P-(3) units, and (only in the case of the x = 25 and 30 glasses) a Gaussian component reflecting phosphate species interacting with five- and six-coordinated silicon species. For 0 <= x <= 25, the decrease in average coordination number may provide the structural explanation for the strong decrease in the glass transition and liquidus temperatures over this composition range, whereas the subsequent increase in T-g at higher P2O5 contents is correlated with the appearance of the higher-coordinated silicon species. While these higher-coordinated silicon species occur within separate microdomains, P-31 spin echo decay spectroscopy suggests that the majority of P atoms tend to be randomly distributed in space, consistent with a statistical P-O-P, Si-O-P, and Si-O-Si connectivity distribution. (AU)

FAPESP's process: 13/23490-3 - Magnetic resonance techniques for the study of Structure/Property correlations in photonic glassy and glass ceramic materials
Grantee:Marcos de Oliveira Junior
Support type: Scholarships in Brazil - Post-Doctorate
FAPESP's process: 13/07793-6 - CEPIV - Center for Teaching, Research and Innovation in Glass
Grantee:Edgar Dutra Zanotto
Support type: Research Grants - Research, Innovation and Dissemination Centers - RIDC