Basic network structure of SiO₂–B₂O₃–Na₂O glasses from diffraction and reverse Monte Carlo simulation

Abstract

Neutron-and high-energy synchrotron X-ray diffraction experiments have been performed on the (75-x)SiO2-xB2O3-25Na2O x=5, 10, 15 and 20 mol% glasses. The structure factor has been measured over a broad momentum transfer range, between 0.4-22 Å -1 . For data analyses and modeling the Fourier transformation and the RMC simulation techniques have been applied. The partial atomic pair correlation functions, the nearest neighbour distances, coordination number distributions and average coordination number values and three-particle bond angle distributions have been revealed. The Si-O network proved to be highly stable consisting of SiO4 tetrahedral units with characteristic distances at rSi-O=1.60 Å and rSi-Si=3.0(5) Å. The behaviour of network forming boron atoms proved to be more complex. The first neighbour B-O distances show two distinct values at 1.30 Å and a characteristic peak at 1.5(5) Å and, both trigonal BO3 and tetrahedral BO4 units are present. The relative abundance of BO4 and BO3 units depend on the boron content, and with increasing boron content the number of BO4 is decreasing, while BO3 is increasing.Keyword: borosilicate glasses, neutron and X-ray diffraction, RMC simulation IntroductionRecently, several experiments have been reported on the study of structure and properties of sodium borosilicate glasses from fundamental and industrial point of view, due to the potential applicability for immobilizing of high-level radioactive wastes, like U-, Pu-, Th-oxides [1-7 and therein]. It has been found that the modifier effect of Na ions influences the ratio of nature of glass network formers Si, B and it is possible to archive a mixed glass network former effect. This effect is believed to have a structural origin, yet a precise understanding of it is still lacking because of the structural complexity of the sodium borosilicate glasses. The structure of borate glasses with alkali oxides has been extensively studied. A nuclear magnetic resonance (NMR) spectroscopy measurements show that the fraction of boron atoms tetrahedral coordinated to the total number of boron atoms varied with the modifier compositions [8][9][10]. By Raman spectroscopy, typical borate groups, such as boroxol, trigonal and tetrahedral units were found to exist in several borate compounds [11,12]. Recently, we have started to examined the atomic structure of a newly prepared three-component sodium-borosilicate system, using a combination of neutron diffraction (ND), high-energy X-ray diffraction (XRD) and reverse Monte Carlo (RMC) modelling that are capable of building threedimensional structure models and so yield a more detailed description of the atomic-scale glass structure. In our previous works we studied the binary sodium silicate glasses (70SiO2-30Na2O) [13], the binary sodium borate glasses (75B2O3-25Na2O) [14] and a five-component sodium borosilicate glass (55SiO2-25Na2O-10B2O3-5BaO-5ZrO2) [15]. Here, we apply the same approach to a ternary

Network Structure and Luminescent Properties of ZnO–B2O3–Bi2O3–WO3:Eu3+ Glasses

“…The B-O coordination was in the range of 3.48 ± 0.05 to 4.00 ± 0.05, and obtained the changes in BO3/BO4 ratio. The boron atoms were coordinated mostly by three and four oxygen atoms, forming trigonal BO3 and tetrahedral BO4 units, in agreement with coordination numbers in SiO2-Na2O-B2O3 glasses [39], in MoO3-ZnO-B2O3 glasses [40], and in ZnO-B2O3-Li2O-Al2O3 glasses [41]. The nearest W-O distances showed characteristic peaks at 1.75 ± 0.05 (Table 3) for both series.…”

Structure of bismuth tellurite and bismuth niobium tellurite glasses and Bi2Te4O11 anti-glass by high energy X-ray diffraction

“…In the present work, the experimentally measured X-ray structure factors (S(Q)) for bismuth tellurite and niobium bismuth tellurite glasses were simulated using the RMC++ soware and partial atomic pair correlation functions, co-ordination numbers, and distribution of bond-lengths and bond angles were determined. 26,[36][37][38][39] RMC uses a threedimensional atomic conguration to t the experimental S(Q) data with the calculated S(Q) and tends to minimize the squared difference between the two S(Q) by the random movement of the atoms in the simulation box. 32,40 As a starting model for each RMC simulation, a random atomic conguration with a simulation box containing a total of 10 000 atoms of Bi, Te, and O for bismuth tellurite system, and 10 000 atoms of Bi, Nb, Te, and O for niobium bismuth tellurite glass system was built using the density data given in Table 1.…”

“…The diffraction data of glasses was analyzed by Reverse Monte Carlo (RMC) simulations, the latter is a powerful tool to study the short-range structural properties such as bond-lengths, bond-angles and the average coordination numbers in disordered materials. 26 The use of high energy X-rays and large area detectors provides access to high values of momentum transfer function, Q with the additional advantage of smaller polarization corrections due to smaller diffraction angles (maximum used 2q $40 ). 27 The diffraction data of the anti-glass sample: 20Bi 2 O 3 -80TeO 2 (Bi 2 Te 4 O 11 ) was analyzed by Rietveld renement in order to obtain the detailed crystal structure information including the Te and Bi co-ordination numbers, the cationoxygen bond lengths and the unit cell parameters.…”

Structure of copper tellurite and borotellurite glasses by neutron diffraction, Raman, 11B MAS-NMR and FTIR spectroscopy

“…(42)(43)(44)(45)(46) The experimental neutron structure factor S(Q) data was obtained and simulated by the RMC method using RMC ++ Version 1. (40,47) The RMC technique minimises the squared difference between the experimental S(Q) and the simulated one from a three-dimensional atomic configuration and partial correlation functions g ij (r) and the neutron scattering weight factors for different correlations were calculated by the following formulas: (48)(49)(50)(51)(52)(53) ij ij , ( ) ( )…”