Borates and borosilicates are potential candidates for the design and development of glass formulations with important industrial and technological applications. A major challenge that retards the pace of development of borate/borosilicate based glasses using predictive modeling is the lack of reliable computational models to predict the structure‐property relationships in these glasses over a wide compositional space. A major hindrance in this pursuit has been the complexity of boron‐oxygen bonding due to which it has been difficult to develop adequate B–O interatomic potentials. In this article, we have evaluated the performance of three B–O interatomic potential models recently developed by Bauchy et al [
- Award ID(s):
- 2034871
- NSF-PAR ID:
- 10484412
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Journal of Non-Crystalline Solids
- Volume:
- 619
- Issue:
- C
- ISSN:
- 0022-3093
- Page Range / eLocation ID:
- 122554
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract J .Non‐Cryst. Solids , 2018, 498, 294–304], Du et al [J. Am. Ceram. Soc. https://doi.org/10.1111/jace.16082 ] and Edèn et al [Phys. Chem. Chem. Phys. , 2018, 20, 8192–8209] aiming to reproduce the short‐to‐medium range structures of sodium borosilicate glasses in the system 25 Na2Ox B2O3(75 −x ) SiO2(x = 0‐75 mol%). To evaluate the different force fields, we have computed at the density functional theory level the NMR parameters of11B,23Na, and29Si of the models generated with the three potentials and the simulated MAS NMR spectra compared with the experimental counterparts. It was observed that the rigid ionic models proposed by Bauchy and Du can both reliably reproduce the partitioning between BO3and BO4species of the investigated glasses, along with the local environment around sodium in the glass structure. However, they do not accurately reproduce the second coordination sphere of silicon ions and the Si–O–T (T = Si, B) and B‐O‐T distribution angles in the investigated compositional space which strongly affect the NMR parameters and final spectral shape. On the other hand, the core‐shell parameterization model proposed by Edén underestimates the fraction of BO4species of the glass with composition 25Na2O 18.4B2O356.6SiO2but can accurately reproduce the shape of the11B and29Si MAS‐NMR spectra of the glasses investigations due to the narrower B–O–T and Si‐O‐T bond angle distributions. Finally, the effect of the number of boron atoms (also distinguishing the BO3and BO4units) in the second coordination sphere of the network former cations on the NMR parameters have been evaluated. -
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Abstract Lithium aluminoborate glasses have recently been found to feature high resistance to crack initiation during indentation, but suffer from relatively low hardness and chemical durability. To further understand the mechanical properties of this glass family and their correlation with the network structure, we here study the effect of adding SiO2to a 25Li2O–20Al2O3–55B2O3glass on the structure and mechanical properties. Addition of silica increases the average network rigidity, but meanwhile its open tetrahedral structure decreases the atomic packing density. Consequently, we only observe a minor increase in hardness and glass transition temperature, and a decrease in Poisson's ratio. The addition of SiO2, and thus removal of Al2O3and/or B2O3, also makes the network less structurally adaptive to applied stress, since Al and B easily increase their coordination number under pressure, while this is not the case for Si under modest pressures. As such, although the silica‐containing networks have more free volume, they cannot densify more during indentation, which in turn leads to an overall decrease in crack resistance upon SiO2addition. Our work shows that, although pure silica glass has very high glass transition temperature and relatively high hardness, its addition in oxide glasses does not necessarily lead to significant increase in these properties due to the complex structural interactions in mixed network former glasses and the competitive effects of free volume and network rigidity.
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Abstract The structures of glasses in the lithium–bismuth orthoborate composition range deviate significantly from the short‐range order structure of the two crystalline end‐members. Although binary Li3BO3and BiBO3are solely of comprised trigonal orthoborate anions, all glasses formed by their combination contain four‐coordinated borate tetrahedra. We analyze the structure of (75−1.5
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Abstract The structure of lithium bismuth borate glasses in the compositional series
x Bi2O3–25Li2O–(75 −x ) B2O3was studied with the use of Raman and infrared (IR) spectroscopies. Transparent glasses formed betweenx = 0 and 55, whereas glass–ceramics formed betweenx = 60 and 75 mol% Bi2O3. Structural investigation on the borate network showed that the glasses were undermodified at high Bi2O3compositions with metaborate, pyroborate, and orthoborate triangles and tetrahedra being present past the stoichiometric orthoborate compositions (O/B = 3). Bi2O3was found to participate in the glass as both a network former and modifier, as observed in the Raman and IR spectra. Optical absorption spectra of the glasses show a redshift of the absorption edge with increased Bi2O3. Optical, thermal, and physical properties of the glasses were examined and correlated to the structural evolution.
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- Journal Article:
- https://doi.org/10.1016/j.jnoncrysol.2023.122554
