NQR Studies of the Structure of Glasses and Crystalline Compounds

Bray, P. J.; Lee, Dong‐Hoon; Mao, De Gen; Petersen, Gary L.; Feller, Steven A.; Bain, D.; Feil, D.; Pandikuthira, Ponnappa; Nijhawan, Sumit

doi:10.1515/zna-1992-1-208

Cited by 8 publications

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“…Magnetic resonance has been used successfully to probe the short-length-scale changes in the network. Bray and co-workers inferred the existence of multiple three- and four-coordinate boron sites in their 10 B NMR spectra, differing in near-neighbor bondingconfigurations. , Using 11 B NQR, they also observed changes in the three-coordinate boron sites in modified borate glasses. ,, We have recently resolved three boron sites in rubidium borate glasses: the three-coordinate boron types present in pure B 2 O 3 and the four-coordinate boron formed by the addition of Rb 2 O . The DAS NMR data show that the increase in four-coordinate boron occurs mainly at the expense of the nonring BO 3 sites.…”

Section: Introductionmentioning

confidence: 89%

Network Modification in Potassium Borate Glasses: Structural Studies with NMR and Raman Spectroscopies

1996

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We have examined the structural changes in the boron−oxygen network that result from chemical modification of glassy boron oxide by potassium oxide. By means of boron-11 dynamic angle spinning (DAS) NMR and Raman spectroscopies, we have identified changes in the structure resulting from conversion of three-coordinate boron to four-coordinate species. We observe coordination changes in two different 3-fold coordinate boron sites: those in six-membered boroxol rings and those in nonring BO3 units. The DAS NMR data show that the fraction of boron in nonring three-coordinate sites decreases as modifier is added. Modification of the boroxol rings is also evident in the Raman data. Assignment of the NMR resonances is made with the help of comparison to spectra of related crystalline potassium borates. Using 11B DAS NMR and 17O magic angle spinning (MAS) NMR, we do not detect significant formation of nonbridging oxygen through 35% added modifier. The changes in the boroxol ring breathing mode in the Raman spectra are attributed to changes in the coordination of the boron that compose the boroxol ring, but coordination changes also occur in the nonring BO3 units. We propose a model that combines these NMR and Raman data, in which modification of both types of 3-fold coordinate sites is included. This model predicts a contribution to the formation of triborate units from nonring BO3 boron, as well as a slightly higher preference for modification of these sites over the boroxol ring boron.

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Section: Introductionmentioning

confidence: 89%

Network Modification in Potassium Borate Glasses: Structural Studies with NMR and Raman Spectroscopies

1996

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“…For all borates studied to date, the value of Q cc for 4-coordinated borons is less than 1 MHz, but 77 can have any value between 0 and 1. Extraction [2,8] of values of Q cc and 77 for the 3-coordinated borons in Li 2 0-2B 2 0 3 will be discussed later in this paper. When the quadrupolar interaction is sufficiently large to require treatment as a second-order perturbation of the Zeeman interaction, the central transition (-1/2 +1/2) is affected [9] and is spread out into the pattern displayed (without inclusion of broadening mechanisms such as the dipole -dipole interaction) in detected without special effort.…”

Section: Introductionmentioning

confidence: 99%

NMR and NQR Studies of Borate Glasses

Bray

Petersen

1998

Zeitschrift Für Naturforschung A

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Nuclear magnetic resonance (NMR) has been used for some 40 years to study atomic arrangements, chemical bonding, and structural groupings in borate glasses and crystalline compounds, and nuclear quadrupole resonance (NQR) has more recently increased the resolution and accuracy of the measurements. Examples are presented of the use of first-order and second-order quadrupolar effects in "B NMR spectra to obtain structural information, and n B and 10 B NQR spectra to obtain the quadrupolar parameters Q cc (the coupling constant) and 77 (the asymmetry parameter) with accuracies of 5 or 6 significant figures, and 3 figures, respectively. Q cc and 77 are extremely sensitive to changes in atomic rearrangements and chemical bonds, so they are excellent monitors and provide identification of bonding configurations and structural groupings in borates: Examples are also presented in which combinations of NMR and NQR data are used to extract the desired information. NQR detection of resonances at frequencies as low as 276 kHz is discussed.

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NQRS Data for Al2O3 (Subst. No. 0064)

Chihara¹,

Nakamura²

2010

Landolt-Börnstein - Group III Condensed Matter

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NQR Studies of the Structure of Glasses and Crystalline Compounds

Cited by 8 publications

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Network Modification in Potassium Borate Glasses: Structural Studies with NMR and Raman Spectroscopies

Network Modification in Potassium Borate Glasses: Structural Studies with NMR and Raman Spectroscopies

NMR and NQR Studies of Borate Glasses

NQRS Data for Al2O3 (Subst. No. 0064)

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