Structural aspects of B2O3-substituted (PbO)0.5(SiO2)0.5 glasses

Abstract

Lead borosilicate glasses having general formulae (PbO)0.5 −x(SiO2)0.5(B2O3)x with 0.0 ≤ x ≤ 0.4 and (PbO)0.5(SiO2)0.5 −y(B2O3)y with 0.0 ≤ y ≤ 0.5 have been prepared by a conventional melt–quench method and characterized by 29 Si, 11 B magic angle spinning (MAS) NMR techniques and infrared spectroscopy, as regards their structural features. From 29 Si NMR results, it has been inferred that with increasing concentration of boron oxide, (PbO)0.5 −x(SiO2)0.5(B2O3)x glasses exhibit a systematic increase in the number of Q4 structural units of Si at the expense of Q2 structural units, along with the formation of Si–O–B linkages. On the other hand, for (PbO)0.5(SiO2)0.5−y(B2O3)y glasses, there is no direct interaction between SiO2and B2O3 in the glass network, as revealed by the 29 Si MAS NMR studies. Boron exists in both trigonal and tetrahedral configurations for these two series of glasses and for the (PbO)0.5(SiO2)0.5−y(B2O3)y series of glasses; the relative concentration of these two structural units remains almost constant with increasing B2O3 concentration. In contrast, for (PbO)0.5−x(SiO2)0.5(B2O3)x glasses, there is a slight increase in the number of BO3 structural units above x = 0.2, as there is a competition between SiO2 and B2O3 for interaction with Pb2+, thereby leading to the formation of BO3 structural units. For both series of glasses, the thermal expansion coefficient is found to decrease with increasing B2O3 concentration, the effect being more pronounced for the (PbO)0.5 −x(SiO2)0.5(B2O3)x series of glasses due to the increased concentration of Q4structural units of silicon and better cross-linking as a result of the formation of Si–O–B-type linkages.

Sol-gel synthesis of NiO nanoparticles doped sodium borosilicate glass with third-order nonlinear optical properties

“…Furthermore, the vibrations of borate network were mainly consisted of structural units like asymmetric stretching relaxation of B-O band of trigonal BO 3 units (1420 cm -1 ), stretching vibrations B-O bond of the BO 4 tetrahedral units (805 cm -1 ) and B-O-B linkages in the borate networks (690 cm -1 ) [30-34]. Beyond that, the sharp peaks around 470 cm -1 (symmetrical bending vibrations of Si-O-Si bond) and the absorption peaks at 1080 cm -1 (asymmetric stretching vibration of Si-O-Si or O-Si-O bond) formed stable silicon network together[35][36][37]. Additionally, Si-O-B vibration peaks (920 cm -1 ) became more intense with the rise in temperature, which could be indicative of the fact that B had been connected to Si-O network.…”

Structural studies on boroaluminosilicate glasses

“…For the glass containing 5 mol% B 2 O 3 ( Fig. 4(a)), the NMR pattern consist of a sharp isotropic peak around À22 ppm along with number of side bands characteristic of tetrahedrally coordinated BO 4 structural units [5,9]. The patterns essentially remained same up to 15 mol% B 2 O 3 (Fig.…”

“…Intensity of the broad peak increases with further increase in B 2 O 3 concentration. The broad peak has been attributed to the trigonally coordinated boron structural units [5,9]. Fig.…”

“…The patterns are almost same except that the intensity of peaks around 3500 cm À1 and 1600 cm À1 are significantly higher for Cu 2+ exchanged sample compared to the unexchanged sample and this has been attributed to the water molecules incorporated into the glass during the room temperature ion exchange process. The peaks around 1050 and 460 cm À1 have been attributed to the stretching and bending vibrations of Si-O-Si/Si-O-B linkages [5,9,13] present in the glass. Photoluminescence measurements were carried out on the samples to check whether any Cu + ions are formed in the glass after ion exchange.…”

“…Solid-state magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy using 29 Si and 11 B as probe nuclei is an ideal technique to monitor the structural changes in borosilicate glasses. For example, incorporation of B 2 O 3 at the expense of PbO in ternary lead borosilicate glasses decreases the thermal expansion coefficient and increases the glass transition temperature [9]. Based on 29 Si and 11 B MAS NMR and infrared (IR) absorption studies, it has been established that formation of Si-O-B linkages and increase in concentration of Q 4 structural units of silicon (where Q n represents silicon structural units having n-number of bridging oxygen atoms) are responsible for the observed variation in the thermal expansion coefficient and glass transition temperature.…”