Non-bridging Oxygen Research Articles

Development of blue-light absorbing silicate glasses through codoping with TiO2, CeO2, Fe2O3, and Bi2O3

The high energy of blue light (approximately 460 nm) emitted from display components may lead to ocular pathologies. Therefore, the development of glass compositions resistant to blue light is crucial. In this study, TiO2, CeO2, Fe2O3, and Bi2O3 were doped into a Na2O–CaO–Al2O3–SiO2 glass composition. The required properties of the glasses are to reduce the transmittance at 460 nm (T460) to less than 50 %, while maintaining high transmittance at longer wavelengths (T550 > 70 %, and T700 > 80 %). The glasses were prepared using the conventional melt-quench method. The cast glasses were analyzed using a UV–visible spectrophotometer to obtain the transmittance spectra ranging from 200 to 800 nm. The reflectance (R) of glass powder compacts was measured using a spectrophotometer equipped with a reflectance integrating sphere. This data was then used to derive the Kubelka-Munk function, F(R), which can display absorption peaks. After deconvolution, the contributions of each doping ion were obtained. Based on the experimental results, the dopant-free glass is colorless, with a cutoff wavelength (λc) of 213 nm and T460/T550/T700 of 90/91/92 %. All four types of dopants increase λc and decrease the transmittance. The combination of Ti–Ce–Fe–Bi dopants is relatively more likely to meet the transmittance requirement. The contributions of Ti4+, Ce4+, Ce3+, Fe3+, and Bi3+ ions to the UV-blue absorption as well as their potential redox tendencies are discussed. Raman analysis reveal that the dopants mainly act as network modifier in the glass structure, increasing the number of non-bridging oxygen. This effect also contributes to the red shift at the absorption edge.

Structural, thermo-mechanical, optical and gamma-ray shielding properties of lead-free BaO–ZnO–B2O3–SiO2 and lead-based PbO–Bi2O3–K2O–SiO2 glasses

Lead-free BaO–ZnO–B2O3–SiO2 glass (BZBS) and lead-based PbO–Bi2O3–K2O–SiO2 glass (LS) were synthesized by melt quench technique. Glass samples were irradiated using 60Co gamma source up to 50 kGy dose to study the changes in structural, thermo-mechanical, optical and gamma ray shielding properties. Measured density values of both the glasses were greater than 4.0 g/cc. X Ray Diffraction (XRD) studies confirmed amorphous nature of prepared glasses before and after gamma irradiation. The structural changes induced by gamma irradiation were also investigated using Raman, Positron annihilation lifetime spectroscopy (PALS) and Electron Paramagnetic Resonance (EPR) spectroscopy. PALS data revealed increase in free volume/voids after irradiation. Defect studies carried using EPR spectroscopy confirmed formation of electron trap centre in BZBS glass, whereas in LS glass in addition to the electron trap centers, non-bridging oxygen hole centers (NBOHC) and peroxy radical defects were also observed. Investigations on thermo-mechanical properties demonstrated higher glass transition temperature (Tg), hardness and modulus of elasticity values for BZBS glass as compared to the LS glass, which were found to be decreased after irradiation because of radiation induced defects. Visible transparency and band gap for BZBS glass were found to be higher than that in LS glass. After irradiation, colour change, reduction in transparency as well as band gap, and red shift in absorption edge were observed due to the formation of defects in both the glasses. The values of radiation induced absorption (α) at three different visible wavelengths have been determined for 50 kGy dose using UV–Vis transmission data. Analysis of refractive index data showed around 12 % reflection losses for both the glasses. Annealing of irradiated samples using UV light source showed significant improvement in transparency. Linear attenuation coefficient (LAC) was calculated using XCOM program and experimentally measured using 60Co 1.33 MeV gamma ray. Linear attenuation coefficient of BZBS glass was around 0.20 cm−1 whereas for LS glass value was 0.24 cm−1. Half value layer thickness of prepared glasses was also compared with available standard materials and it was found that prepared glasses may be suitable for shielding of high energy gamma rays.

Study on Micro Structural Properties of Alkali - Doped SiO2 Melt Using Molecular Dynamics Simulation

Molecular dynamics (MD) simulation could provide details about local microstructure at atomic level, so we use this method to investigate micro-structural properties of sodium in Na2O-doped SiO2 melt. Additionally, we calculated the Voronoi polyhedrons to determine the spatial distribution of atoms in the simulation models. The result shows that many bridging oxygen (BO) polyhedrons and all Si-polyhedrons do not contain Na atoms. Most non-bridging oxygen (NBO) polyhedrons contain 2, 1 or no Na atoms, where BO, NBF is the O bonded with 2 and 1 or no Si, respectively. Average volume per polyhedron decreases in order: NBFx-polyhedron ® BOx-polyhedron ® Six-polyhedron. Na atoms are found in NBFx-polyhedrons and frequently move through them leading to very fast diffusivity of Na in comparison with Si and O. The simulation shows that the number of neighbors around the NBFx-polyhedron is larger than that around the BOx-polyhedron.

Mechanical and Electrochemical Properties of Lithium Aluminoborate Glasses

The elastic moduli and the indentation behavior of glasses from the xLi2O-5Al2O3-(95−x)B2O3 system, with x = 35, 40, and 50 were characterized. Glasses become softer and less resistant to indentation cracking as the lithium content is increased, as a result of increasing the numbers of 3-fold coordinated boron and non-bridging oxygen atoms in this composition range. In parallel, the ionic conductivity at 25 °C is increased from 3.7 10–10 to 5.5 10–8 S∙cm–1, and the activation energy, as measured in the 10 to 90 °C ranges is between 55 (50 % Li2O) and 65 (35 % Li2O) kJ∙mol–1, which shows that the ionic diffusion of lithium is easier in Li-rich compositions. Measurements of the conductivity under a compressive load aligned with the electric field revealed a mechanical-electrical coupling. The change of the activation energy with the stress is associated with an activation volume, and thus a stress sensitivity, that is increased with the lithium content.

Influence of sodium oxide substitution on structural and gamma-ray radiation shielding properties of sodium borosilicate glass

In this paper, borosilicate glasses with varying concentrations of sodium oxide were synthesized using the melt-quenching method. The amorphous nature of the glasses under investigation, with a composition of (20 + x)Na2O-(60-x)B2O3–20SiO2 (where x = 0, 3, 5, 7, 8, 10, 13, 15, 17, and 20 mol%), was confirmed through X-ray diffraction (XRD) analysis. Fourier-transform infrared (FT-IR) spectroscopy was employed to analyze the glasses and revealed an increase in the concentration of non-bridging oxygen atoms (NBO) with increasing amounts of Na2O. The N4 parameter, which represents the fraction of NBOs, was calculated and found to decrease from 74% to 52% as the concentration of Na2O increased. The density of the glasses increased from 2.391 g/cm3 to 2.744 g/cm3 when B2O3 was replaced with Na2O, while the molar volume decreased from 27.68 cm3/mol to 23.56 cm3/mol. Theoretically, theoretical calculations were performed using newly developed computer software called Phys-PSD to assess their shielding properties, including attenuation coefficients, half value layer, and buildup factors. The calculations were conducted in the energy range of 0.015–15 MeV. The results indicated that the synthesized glasses exhibited promising potential as radiation shields.

Spectroscopic properties of Pr3+-doped Titania-Silicate glass ceramic for photonic applications

Silicate-Titania (SiTi) glass-ceramics doped with Pr3+ (0.6, 1.6, 2.4 and 3.6 mol%) ions were prepared by sol-gel technique. The materials were characterized by powder XRD, FTIR, TEM, EDX, Optical absorption and Photoluminescence spectroscopy. The identification of non-bridging oxygen (NBO) formation and the removal of OH groups are validated through analysis of the FTIR spectra. Additionally, measurements using XRD and TEM showed that the samples contain nano-sized crystallites. The three phenomenological Judd–Ofelt (J–O) intensity parameters Ω2, Ω4, and Ω6 were obtained and used to analyze different radiative characteristics for the fluorescence levels of Pr3+ in the glass ceramic, including radiative lifetime, branching ratio, radiative transition probability and stimulated emission cross-section. Several emissions were observed in the visible region, among which the 1D2→3H4 in the orange-red region is the most intense. All of these reported branching ratios, stimulated emission cross-sections, and visible emission spectra point to the possibility of employing them as red region lasers. The CIE chromaticity coordinates from all of the emission spectra were also assessed to determine if these materials are suitable for orange-red phosphors. According to CIE chromaticity investigations, 1.6 mol% of Pr3+ ion concentration is ideal for SiTiPr glass-ceramic for use as red phosphors and possibly red lasers.

Synergistic optimization of physical, thermal, structural, mechanical, optical and radiation shielding characteristics in borate glasses doped with Bi2O3

This paper presents the effect of Bi2O3 on physical, thermal, structural, mechanical, optical, and radiation shielding properties of borate-based glasses having a composition (60-x)B2O3–25Na2O–13BaO-2Gd2O3-xBi2O3; x = 0, 5, 10, 15, and 20 mol%. XRD analysis confirms the amorphous structure of the prepared glasses. As Bi2O3 content increases from 0 to 20 mol%, density of the glasses increases from 2.729 to 3.896 g/cm3, and molar volume rises from 30.947 to 42.017 cm3/mol. The glass transition temperature (Tg) of the samples decreased with Bi2O3 content. FTIR analysis reveals the presence of BO3, BO4, BiO3, and BiO6 structural units in the prepared glasses. Optical absorption studies indicate a decrease in band gap energy from 3.006 to 2.573 eV for indirect transitions implying non-bridging oxygen atom formation and this inference is supported by both physical and FTIR results. The elastic parameters, derived from Makishima-Mackenzie model decreased with increased Bi2O3 concentration suggesting a reduction in mechanical properties. The mass attenuation coefficient (μm), determined through experimental measurements and using Phy-X/PSD software, yielded closely aligned values. Other shielding parameters such as half-value layer (HVL), mean free path (MFP), and effective atomic number (Zeff) were also calculated. The glass containing 20 mol% Bi2O3 exhibited a significant gamma-ray shielding potential due to its high μm value, (0.1260 cm2/g at 0.511 MeV and 0.0960 cm2/g at 0.662 MeV) and Zeff together with low HVL and MFP. A Comparative analysis of the μm values for the present glasses and that of other glasses containing Bi2O3 is also presented.

Effect of Al2O3/Ga2O3 ratio on the structure and luminescence properties of Sm3+ doped SrO-Nb2O5-Al2O3-Ga2O3-SiO2 glasses

The Sm3+ doped SrO-Nb2O5-Al2O3-Ga2O3-SiO2 glasses in this work were prepared using the conventional melt quenching method. The effects of Al2O3/Ga2O3 ratio on the structure and orange light emission properties were studied by XRD, Raman spectroscopy, spectrophotometer and J-O theory, respectively. With the increase of Al2O3 content, the absorption coefficient of the glass sample gradually increases, which might be attributed to an increase in non-bridged oxygen bonds caused by a change in the glass network structure. Under 403 nm excitation, the emission spectra show clear peaks at 602 nm and 649 nm, representing the 4G5/2 → 6H7/2, and 4G5/2 → 6H9/2 transitions, respectively. When the Al2O3/Ga2O3 ratio is 0.25, the sample luminescence intensity is the highest, and the emission cross section of A2 glass sample is 4.34 × 10−22 cm2. The CIE color coordinates, color purity, and color temperature values of all samples were determined, and they were all located in the orange-red light region. The experiments results reveal that the prepared silica-aluminum-gallium glasses has a potential application prospect in orange-red LEDs, solid state lasers and other fields.

Sub-Nanometer-Range Structural Effects From Mg2+ Incorporation in Na-Based Borosilicate Glasses Revealed by Heteronuclear NMR and MD Simulations.

Magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) experiments and molecular dynamics (MD) simulations were employed to investigate Na2O-B2O3-SiO2 and MgO-Na2O-B2O3-SiO2 glass structures up to ≈0.3 nm. This encompassed the {Na[p]}, {Mg[p]}, and {B[3], B[4]} speciations and the {Si, B[p], M[p]}-BO and {Si, B[p], M[p]}-NBO interatomic distances to the bridging oxygen (BO) and nonbridging oxygen (NBO) species, where the superscript indicates the coordination number. The MD simulations revealed the dominance of Mg[5] coordinations, as mirrored in average Mg2+ coordination numbers in the 5.2-5.5 range, which are slightly lower than those of the larger Na+ cation but with a narrower coordination distribution stemming from the higher cation field strength (CFS) of the smaller divalent Mg2+ ion. We particularly aimed to elucidate such Na+/Mg2+ CFS effects, which primarily govern the short-range structure but also the borosilicate (BS) glass network order, where both MD simulations and heteronuclear double-resonance 11B/29Si NMR experiments revealed a reduction of B[4]-O-Si linkages relative to B[3]-O-Si upon Mg2+-for-Na+ substitution. These effects were quantified and discussed in relation to previous literature on BS glasses, encompassing the implications for simplified structural models and descriptions thereof.

DFT study of the role and possible contribution of defects to lithium metasilicate [formula omitted] luminescence

Lithium metasilicate (Li2SiO3) has recently been shown to display outstanding stimulated luminescence properties, which are governed by defects and/or impurities. Here, the possible contribution and character of native point and complex defects to stimulated luminescence of lithium metasilicate have been investigated employing calculations based on the density functional theory (DFT). Under high concentrations of acceptor defects, isolated lithium interstitials were found to be the defects with the lowest formation energy (0.41 eV) but it is shown that they cannot contribute to luminescence. On the other hand, Oi−2 are the most favorable and stable defects under high concentrations of donor defects. F-centers and oxygen peroxides were identified as first- and second-order processes of point defects, which would explain experimental observations in the literature. Bridging oxygen vacancies were shown to introduce shallow electron traps able to trap up to four electrons. On the contrary, non-bridging oxygen vacancies lead to the formation of deep color centers with the capability of trapping up to two carriers/center, which could be the final state for the radiative process of luminescence. These results provide guidance for the interpretation of experimental measurements of luminescence.

An investigation of the structural and optical properties of modified barium magnesium fluoroborate glasses with hafnium oxide (HfO2)

AbstractGlasses of nominal composition xHfO2–(35-x)B2O3–15MgF2–35BaO, where x ranged from 0 to 0.2 mol% were fabricated using a melt-quenching technique. Structural characterization techniques, including X-ray diffraction (XRD), Fourier-transform infrared (FTIR) spectroscopy, and Raman spectroscopy, were employed to elucidate the glass network structure. The XRD patterns confirmed the amorphous nature of the studied glasses, while the FTIR and Raman spectra revealed that the incorporation of HfO2 may led to a transformation of trigonal BO3 units to tetrahedral BO4 units in the borate glass network. Deconvolution analysis of the FTIR and Raman bands provided quantitative insights into the extent of this structural rearrangement as a function of HfO2 content. UV–Vis absorption studies demonstrated that the optical bandgap of the glasses was widened with increasing HfO2 additions. This blue shift in the absorption edge was attributed to the increased formation of bridging oxygen bonds and reduced non-bridging oxygen content in the glass network. The results indicate that the studied glasses exhibit excellent compositional tunability through the incorporation of HfO2. The structural modifications and concomitant optical property enhancements suggest the potential of this glass system for various integrated photonic applications where low phonon energy and tailored transparency are highly desirable. The present work introduces a comprehensive investigation of the structural and optical property modifications in barium magnesium fluoroborate glasses induced by the addition of hafnium oxide (HfO2).

Tb3+ doped silicoborate glass scintillator for high resolution synchrotron X-rays imaging application

This research aims to develop a combination of SiO2 and B2O3 glass former (called, silicoborate glass) to be used as a scintillation material for digital radiography application. The silicoborate glass doped with different concentration of Tb2O3, xTb2O3–7.5Gd2O3–40Na2O–5SiO2– (47.5-x)B2O3, where x = 0, 1, 2, and 3 mol% (xTb:7.5Gd) were prepared by melting and then rapid quenching in graphite mold. The density of the prepared glasses was high with Tb2O3 concentration, indicating that the glass became denser and could strongly interact with X-rays. The molar volume increased with Tb2O3 concentration, suggesting the increase of Non-Bridging Oxygen (NBOs) in glass matrix. The xTb:7.5Gd glasses absorbed photons in visible and near-infrared regions and was observed that the absorption bands increased with Tb2O3 concentration, which was the result of the 4f6-4f6 transitions behavior of Tb3+ ions. The photoluminescence and radioluminescence results revealed the distinct emission occurring at 544 nm (5D4→7F5). The photoluminescence quantum yield (PLQY) of glass had the maximum efficiency at 30.85%. The luminescence peak area under X-rays excitation glass was maximum at 109% of BGO crystal. CIE 1931 chromaticity of the xTb:7.5Gd glasses showed the color coordinates in yellowish-green area. The decay time of the xTb:7.5Gd glasses were in the millisecond range for different excitations. The probability of energy transfer was investigated between Gd3+ and Tb3+ ions in glass and may occur mainly between the 6P7/2 level of Gd3+ and 5H7 level of Tb3+. The X-rays imaging using the developed glass as a scintillator was performed by Synchrotron X-rays and the spatial resolution 6 lp/mm was achieved. These results demonstrate that the 3 mol% of Tb2O3 doped silicoborate glass can be used as a scintillator and can be applied for a high-resolution Synchrotron X-rays imaging system.

Insight into the TiO2 on transport behavior and heat transfer of the CaO–SiO2–FeO–MgO system at different basicities: Molecular dynamics simulation and thermodynamics

In order to promote the resource utilization of Ti-containing converter slag and reduce the loss of metallic Ti, it is necessary to clarify the relationship between the oxygen network structure and thermophysical properties of the slag. The present work uses classical molecular dynamics (CMD) simulation to study the effects of basicity (1.0–3.0) and TiO2 content (0%–10 %) on the local structural properties, viscosity, and thermal conductivity of the CaO–SiO2–FeO–MgO–TiO2 (CSFMT) system at 1873 K. The M − O (M = Ca, Si, Fe, Mg, and Ti) bond length calculated based on CMD is consistent with the experimental results, and the [SiO4] tetrahedron and [TiO6] octahedron are the basic structural units of the CSFMT system. The increase in basicity promotes the break of bridging oxygen (BO) Si–O–Si and the formation of non-bridging oxygen Si–O-M. The increase in TiO2 content promotes the formation of Ti–O–Si in the system. The basicity and TiO2 content affect the thermophysical properties of the CSFMT system by promoting and inhibiting the depolymerization of the oxygen network structure, respectively. The diffusion abilities of different atoms in the CSFMT system are in descending order of Fe > Mg > Ca > O > Si > Ti. The viscosity of the CSFMT system decreases with increasing basicity and increases with increasing TiO2 content. Increasing the proportion of BOs can weaken the anharmonicity in the polyhedral structural units and reduce phonon scattering. With increasing basicity and TiO2 content, the effective phonon mean free path decreases and increases, respectively, resulting in a decrease and an increase in the thermal conductivity of the CSFMT system. The changes in the microstructure properties of the CSFMT system can be reasonably explained by the changes in its thermodynamic properties such as enthalpy. It is worth noting that the basicity has a greater effect on the viscosity, while the TiO2 content has a more significant impact on the thermal conductivity of the CSFMT system.

Er3+/ Yb3+ co-doped multi-functional silica phosphate glass films for integrated photonic applications

The multi-component silicate glasses co-doped with Er3+/Yb3+ were fabricated as thin films by the spin coating technique, which was analyzed for their optoelectronic response. Their monolith counterparts synthesized by the sol-gel route were used for the electrical studies. The films evidenced nanocristobalite phases at low levels of doping. The film micrographs explicated gas-trapped circular dimensions on the surface, due to the spreading of the sol on the substrate during the spin coating process. The glasses show a decrease in the number of polarizable non-bridging oxygen units with doping, reducing the polarizability and optical basicity. The films exhibit prominent green lasing in the downshifting process. The energy transfer from the Yb3+ ions endows the glasses with significant red lasing, suppressing the green emissions by the upconversion mechanism, which is also validated by the colorimetric chromaticity analysis. The gain cross-section of the glass doped with 1.5 mol% of Yb3+ is 23.3 × 10−20 cm2 in the S-band telecommunication domain. The glass film evidences its potential for NIR lasers, beyond a population inversion of 40 %, and a decreasing metastable lifetime of 6.6 μs. Beyond 1.5 mol% of the co-dopant Yb3+, energy transfer dominates, due to the dipole-quadrupole interactions, which has been corroborated by the Inokuti-Hirayama model. The conductivity in the glasses shows a decreasing trend with doping. The Randle's equivalent circuitry of the Nyquist impedance plots, predicts Warburg diffusion impedance that deters the space charge polarization. The consequential decrease in the dielectric constant and capacitance makes the glasses suggestive of multi-layer dielectric substrates in the integrated microelectronic technology for soldering of the printed circuit boards (PCB) that demand low signal losses.

Effect of basicity on the structure and viscosity properties of HIsmelt slag: A molecular dynamics simulation

ABSTRACT HIsmelt is an emerging and potentially promising non-blast furnace ironmaking process, and the characteristics of its slag are crucial to the smelting process. Currently, there is no atomic-scale research on the slag of the HIsmelt process. In this work, molecular dynamics simulations were employed to investigate the effect of basicity on the structure and viscosity properties of the HIsmelt CaO-SiO2-Al2O3-FeO slag system at 1773 K. The slag structure was characterised by calculating structural parameters, including radial distribution function, coordination number, oxygen type, and bond angle distribution. Furthermore, the viscosity of the slag system was estimated by using the self-diffusion coefficient and compared with mathematical models. The results indicate that basicity has a negligible impact on the short-range ordering of aluminosilicates in the HIsmelt slag system. As slag basicity increases from 0.4 to 1.8, the concentration of bridging oxygen decreases, non-bridging oxygen increases, and the [SiO4]4+ and [AlO4]5+ network structures undergo depolymerisation in the system. Additionally, the self-diffusion coefficient of atoms increases, and the slag viscosity exhibits a declining trend with increasing basicity. In the basicity range of 0.8 −1.8, the current MD simulations align with the results of the previous models.

Intrinsic influence of the stress on the optical properties of Panda-type erbium-doped fibers.

In this study, erbium-doped fiber (EDF) and Panda-type polarization maintaining erbium-doped fiber (PM-EDF) were fabricated from the same erbium-doped preform. The intrinsic influence of stress induced by the Panda-type design on the optical properties was investigated. A local structural model of EDF was developed to simulate the introduction of stress by varying the length of non-bridging oxygen (NBO) bonds between erbium ions (Er3+) and the silica network, providing theoretical insights. An increase in bond length (indicative of tensile stress), results in decreased excitation and emission intensities for EDF, and the peaks exhibit redshifts. Conversely, a decrease in bond length (indicative of compressive stress), leads to increased excitation and emission intensities, with the peaks showing blueshifts. Experimentally, PM-EDF demonstrated a lower absorption coefficient compared to EDF, with absorption peaks experiencing redshifts of approximately 2 nm. Furthermore, the emission intensity was diminished, and the emission peak at 1530 nm displayed a redshift of around 3 nm. The fluorescence lifetime was shortened to 9.99 ms. Additionally, the total gain of PM-EDF decreased by approximately 4 dB, and the bandwidth narrowed by roughly 13%. The experimental outcomes largely align with the simulation predictions, further corroborating the significant impact of stress on the optical properties of PM-EDF.

Synthesis and optical properties of novel Bi2O3–Li2O–Al2O3–TeO2 glasses

Quaternary glasses of xBi2O3–20Li2O–5Al2O3–(75-x)TeO2 with varying compositions were produced by melt quenching. The purpose was to investigate their physical and optical characteristics. FTIR analysis was employed to examine the structural features of the glass system, followed by UV–Vis spectroscopy for verification of its optical properties. Density measurements performed with a densitometer revealed a rise from 4.68 g/cm³ to 5.06 g/cm³ as the Bi2O3 concentration increased. The refractive index value elevated from 2.6731 to 2.6975 alongside a notable rise in the Urbach energy range from 0.46 to 0.96 eV. As the amount of Bi2O3 varies from 0 to 5 mol%, there was a corresponding rise in the presence of BiO6 units associated with non-bridging oxygen atoms. This observation coincided with a weakening of the bismuth single bond strength, dropping from 283.54 kJ/mol to 158.71 kJ/mol. The optical transmittance decreases to 0.6518, while the reflection loss increases to 0.2108, with an increase in bismuth concentration from 0 to 5 mol%. As the bismuth content increases, both the polarizability of oxide ions and their optical basicity rise consistently, with polarizability values increasing from 2.9163 to 3.0910 Å3 and optical basicity values climbing from 1.0974 to 1.1297. The calculation of interaction parameters indicated that the inclusion of Bi2O3 in glass samples resulted in a shift from high covalency to ionicity, attributed to Bi2O3 acting as a glass modifier.

Structural and elastic properties of zirconium silicate glasses: Insight from molecular dynamic simulation

Using Morse potentials, we performed molecular dynamics simulations to study the effect of ZrO2/SiO2 substitution on the structure and mechanical properties of SiO2-ZrO2 glasses with various ZrO2 concentrations (5, 10, 20, 30, 40, and 50 mol%). We computed the pair distribution function (PDF) for all atomic pairs and extracted the cation-oxygen coordination number and bond distance as a function of composition for Zr4+ and other cations. We found that Zr entered the glass network as distorted [ZrO6] octahedra. Our results showed that the ZrO2 content was positively associated with the number of non-bridging oxygens and the emergence of tricluster oxygens, which consequently reduced the glass transition temperature. The elastic constants such as Young’s, bulk and shear modulus, increase with rising zirconium content.

Influence of high-pressure on the short-range structure of Ca or Na aluminoborosilicate glasses from 11B and 27Al solid-state NMR

The present study investigates the boron and aluminium speciation of aluminoborosilicate glasses synthesised under ambient to high-pressure conditions (up to 2.0 GPa) using 11B and 27Al Nuclear Magnetic Resonance. Four glass series were prepared in the SiO2-Al2O3-B2O3-Na2O/CaO system, with either high or low R' values (R'=([Na2O]+[CaO])/([B2O3]+[Al2O3])). 11B NMR reveals a linear increase in four-coordinated boron (BO4) with pressure for Ca glasses and non-linear with a plateau between 0.5 and 1.5 GPa for Na glasses. 27Al NMR reveals minimal pressure impact on aluminium coordination in sodium glasses. Conversely, calcium glasses form higher-coordinated AlO5 and AlO6 units under pressure. The determination of non-bridging oxygen (NBO) variation witnesses the change in compensation mechanism for boron species. In low R' glasses, limited NBOs suggest Na+/Ca2+ release from AlO4 as the primary compensation source. This work sheds light on pressure's influence on network connectivity in simple glasses, aiding the understanding of complex glass behaviour.

Exploring the interplay of structure, optical, magnetic and radiation shielding properties in GeO2/Bismuth borate glasses

This article investigates the structural, chemical, optical, and magnetic properties of borate bismuth glasses doped with increasing GeO2 concentrations. X-ray diffraction (XRD), Raman spectroscopy, density measurements, thermal analysis, UV–Vis absorption, and VSM studied the impact of GeO2 on the glass network. The XRD results of the study confirmed that glass is amorphous. The bulk density increased while the molar volume decreased with increasing GeO2 concentration. Glass transition temperature (Tg) slightly decreases due to weaker Ge–O bonds and lower cross-linking density. Crystallization temperature (Tc) increased as GeO2 disrupts the network, hindering crystal nucleation and growth. Optical band gap narrows with increasing GeO2, with direct and indirect gaps decreasing. Urbach energy (EU) rises with GeO2, indicating increased disorder in the glass network. Refractive index (n) and extinction coefficient (k) both increased with GeO2, attributed to non-bridging oxygen formation. VSM measurements reveal an increase in saturation magnetization from 0.1 to 0.3 emu/g with increasing GeO2 content. Mass attenuation coefficient (MAC) and linear attenuation coefficient (LAC) investigations showed the efficiency of the glass system for radiation attenuation at varying energies. The unique properties of these borate bismuth glasses doped with GeO2 show promise for various technological advancements in optoelectronics and radiation shielding.