Structural study of Mg‐bearing sodosilicate glasses by Raman spectroscopy

Abstract

The presence of magnesium in glasses of geological, medical, and technological interests influences their physicochemical and durability properties. However, the understanding of the role of magnesium is dependent on the combined knowledge of the structural environment of magnesium in the glass or melt and of the silicate network connectivity of the studied systems. In this article, we present a Raman spectroscopic study of the network connectivity of 10 ternary silicate glasses in the system Na 2 O-MgO-SiO 2 and one Mg-free binary silicate glass Na 2 O-SiO 2 . Results obtained at constant polymerization suggest the existence of various Q n units according to the nature of the modifying cation. As polymerization decreases for Na 2 O-MgO-αSiO 2 glasses (labeled as NMSα with α decreasing from 10 to 2), the band associated with Si-O-Si bending in fully polymerized region disappears being gradually replaced by a band attributed to Si-O-Si bending in region containing mainly Q 2 and Q 3 species. For highly polymerized glasses (NMS10-NMS4), the coexistence of these two bands suggests the presence of two interconnected networks. Concomitantly, the signal associated with Q 3 species first increases. For a further decrease of the polymerization, the high wavenumber part of the signal associated with Q 3 species decreases, while the intensity of the high wavenumber part of the band related to Q 2 species increases. This result strongly suggests that magnesium charge-balances preferentially Q 2 species rather than Q 3 species.

Vanadium in Borosilicate Glass

“…The bands appearing in the range 200–850 cm −1 are assigned to Si–O–Si bending of Si against tetrahedral cage with slight displacement of oxygen . Bands at 495 cm −1 (485 cm −1 in this study) and 435 cm −1 are assigned to SiO 4 tetrahedra associated with one bridging oxygen, while the one at 530 cm −1 is due to SiO 4 tetrahedra associated with non‐bridging oxygen . Published data from borosilicate glasses suggest that peaks observed around 950, 1075, and 1120 cm −1 are due to Q 4 Si–O stretching, Q 3 Si‐O − Na + stretching, and to Q 2 Si–O − Na + , respectively .…”

Particular H2O dissolution mechanism in iron‐rich melt: Application to martian basaltic melt genesis

“…Hence, we attributed Q 4 at 1,080 cm −1 , Q Si─O─Si at~1,020 cm −1 , Q 3 at~950 cm −1 , and Q 2 at~880 cm −1 . The Q Si─O─Si corresponds to the vibration of the interconnected oxygen between two tetrahedral Q n units as stated in previous studies, [86,87] although Trcera et al [88] assigned it to Q 3 species. Considering the work of Micoulaut et al [89] and Mysen, [90] and the low NBO/T of our glasses (i.e., <1), Q 1 species cannot be present.…”

A Raman spectroscopic study of glass trade beads excavated at Mapungubwe hill and K2, two archaeological sites in southern Africa, raises questions about the last occupation date of the hill

“…Another difference in the spectra is that in the spectrum of the Mapungubwe Oblate two peaks (or shoulders) can be distinguished around 952 and 987 cm À1 , while in the spectrum of the typical K2 bead only one peak at 990 cm À1 is observed. It has been shown that the presence of magnesium in glasses give rise to an extra peak in the Raman spectrum in this region e the exact position dependent on the composition of the glass (Trcera et al, 2011).…”