Structure Of Borate Glasses Research Articles

Significantly improved optical and radiation transmission performance of borate glasses via Tb and Yb rare earth doping

The present study was intended to present new borate glass structure with attractive properties useful for optical and radiation shielding purposes. Therefore, a novel series of B2O3-glass samples defined as: 75B2O3 – 10Li2O – (15-x-y)PbO – x(Yb2O3) – y(Tb2O3), where the corresponding oxide fractions are expressed in mol percent and x and y varied between 1 and 2 mol%, were prepared by employing the well-known melting-and-quenching technique. The structural, physical, optical, and radiation interaction qualities of the glasses were probed based on established experimental and theoretical processes. There was a thin line between the density and molar volumes of the glasses, fluctuating between 3.168 and 3.224 g/cm3 and 28.602 and 29.117 cm3/mol, respectively. All the glass samples exhibited a transparency of over 80 % in the visible range and most parts of the infrared spectrum. The analysis of the gamma photon interaction parameters showed that density and chemical composition greatly influence the shielding abilities of the glasses. The mean free paths of the studied glasses were lower than some known shielding glasses and other materials. The value of ΣR for 1Y0T, 1Y1T, 1Y2T, and 2Y1T is 0.1059, 0.1066, 0.1051, and 0.1063 cm−1, respectively. The half value layers of the glasses had almost a constant minimum value of 0.005 cm at the minimum energy (0.015 MeV) and maximum values of 7.192, 7.100, 7.152, and 7.035 cm for 1Y0T, 1Y1T, 1Y2T, and 2Y1T, respectively at 10.000 MeV. The glasses are potentially more effective for radiation shielding and also desirable where there is lack of space for thicker shield designs. The present glasses had better fast neutron moderating capacities compared to some conventional moderators. None of the studied borate glasses showed a clear performance advantage to the others in terms of absorbing electrons, protons, alpha particles and heavy carbon ions. The studied borate glasses are recommended as transparent and effective radiation protection barriers in ionizing radiation facilities.

Optical parameters and gamma shielding quality of sodium-borate glasses: The relative contribution of Bi2O3, SrO, and Li2O

The optical quality and compositional flexibility of borate glasses make them attractive materials for optical applications, nuclear waste containment, transparent radiation shields and many other applications in the nuclear and allied industries. This study presents the physical, optical, and gamma transmission data of the sodium borate glass structure: 75B2O3 – 15Na2O – 9.5x – 0.5Nd2O3; for x = Bi2O3 (BiNd), SrO (SrNd), and Li2O (LiNd). The glasses were prepared using the traditional melt-and-quench technique. The influence of Bi2O3, SrO, and Li2O on the physical attributes, optical constants, and gamma radiation interaction coefficients was probed using standard laboratory procedures and software. The density of BiNd, SrNd, and LiNd was 3.32, 2.43, and 2.24 g/cm3, respectively. The molar volume of the glasses followed the trend: BiNd > SrNd > LiNd. The optical constants of the glasses, such as refractive index, metallization criterion, molar refractivity, molar polarizability, reflectance loss, and optical transmission, showed a wide fluctuation with respect to glass composition. The values of the gamma mass attenuation coefficients for 15 keV–15 MeV photons were in the range 0.0316–45.0225 cm2/g for BiNd, 0.0206–5.4940 cm2/g for SrNd, and 0.0184–3.4603 cm2/g for LiNd. Generally, density has a positive correlation with the gamma absorption prowess of the investigated xNd glasses. A correlation between the optical and shielding parameters was highlighted in this study. The xNd glasses, especially SrNd and BiNd, are preferred as transparent radiation protection barriers, in contrast to some conventional Pb-based glasses, from environmental and public health perspectives. This glass composition is therefore unique and its properties are essentially useful in optical and radiation technologies.

Sn2+/Pb2+ Doping‐Induced Highly Transparent Boroaluminate Microcrystalline Glass With Deep Traps for Long‐Term Optical Storage and Time‐Lapse X‐ray Imaging

AbstractThe development of microcrystalline glass‐ceramics with high transparency and deep trap energy levels is crucial for the cost‐effective and large‐scale production of scintillators and optical data storage applications. In this study, the incorporation of highly electronegative divalent tin (Sn2+) plays a key role in modulating the network structure of borate glass. This leads to the successful synthesis of SrAl2O4:Eu2+ microcrystalline glass with high transparency, reaching up to 80%, and excellent crystallinity. Additionally, a series of non‐optically active ions with different valence states is co‐doped with Eu2+ to fine‐tune the trap levels of the SrAl2O4 microcrystals. All samples maintain high crystallinity and exhibit good transparency. In particular, the Pb2+ ion co‐doped samples achieve an increased trap energy level of 1.28 eV, significantly enhancing their capacity to capture X‐rays and ultraviolet light. Density functional theory calculations reveal that this enhancement is due to severe lattice distortion caused by Pb2+ ions occupying interstitial sites in SrAl2O4. Utilizing the SrAl2O4:Eu2+, Pb2+ glass‐ceramics materials, X‐ray imaging with a delay of up to 210 s and optical information storage for >60 d is achieved. This study provides valuable insights into the crystal growth and trap modulation of persistent luminescent materials within a three‐dimensional glass network structure.

Effect of the Addition of WO3 on the Structure and Luminescent Properties of ZnO-B2O3:Eu3+ Glass.

Glasses with the compositions in mol % of 50ZnO:(50 - x)B2O3:0.5Eu2O3:xWO3, x = 0, 1, 3, 5 and 10 were obtained by applying the melt-quenching method and investigated by Raman spectroscopy, DSC analysis and photoluminescence (PL) spectroscopy. Raman spectra revealed that tungstate ions incorporate into the base zinc borate glass as tetrahedral [WO4]2- groups, and octahedral [WØ4O2]2- species with four bridging and two non-bridging oxygen atoms. There are also metaborate, [BØ2O]- and pyroborate units, [B2O5]4-, in the glass networks. The glasses are characterized by good transmission in the visible region, at about 80%. Photoluminescence (PL) spectra evidenced that WO3 is an appropriate constituent for the modification of zinc borate glass structure and for enhancing the Eu3+ luminescent intensity. The most intense luminescence peak observed, at 612 nm, suggests that the glasses are potential materials for red emission.

Structure and Luminescent Properties of Niobium-Modified ZnO-B2O3:Eu3+ Glass.

The effect of the addition of Nb2O5 (up to 5 mol%) on the structure and luminescent properties of ZnO-B2O3 glass doped with 0.5 mol% (1.32 × 1022) Eu2O3 was investigated by applying infrared (IR), Raman and photoluminescence (PL) spectroscopy. Through differential thermal analysis and density measurements, various physical properties such as molar volume, oxygen packing density and glass transition temperature were determined. IR and Raman spectra revealed that niobium ions enter into the base zinc borate glass structure as NbO4 tetrahedra and NbO6 octahedra. A strong red emission from the 5D0 level of Eu3+ ions was registered under near UV (392 nm) excitation using the 7F0 → 5L6 transition of Eu3+. The integrated fluorescence intensity ratio R (5D0 → 7F2/5D0 → 7F1) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites. The higher Eu3+ luminescence emission observed in zinc borate glasses containing 1-5 mol% Nb2O5 compared to the Nb2O5-free zinc borate glass evidences that Nb2O5 is an appropriate component for modifying the host glass structure and improving the emission intensity.

Fabrication of novel BaO–Al2O3–Bi2O3–B2O3 glass system: Comprehensive study on elastic, mechanical and shielding properties

The influence of barium oxide to the elastic and shielding properties of alumina bismuth borate glass system with the compositions (BaO)x(Al2O3)0.05 (Bi2O3)0.3 (B2O3)0.65-x where x = 0, 0.05, 0.10, 0.15, 0.20, 0.25, 0.30 mol% and classified as G1, G2, G3, G4, G5, G6 and G7 were investigated. The elastic properties of the glass system were examined by bulk density, molar volume, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy and non-destructive ultrasonic velocity measurement. The experimental results show that the density of the glass sample increase and molar volume of the glass sample was decrease. The XRD analysis revealed that the glass sample shows the characteristics of the amorphous nature without any sharp lines or peaks while the FTIR revealed the major broad absorption bands for borate glass structure. The ultrasonic velocities and elastic moduli measurement shows an increasing trend with the addition of BaO. The mass attenuation coefficient (MAC) demonstrated that the presence of BaO enhances the MAC values, resulting in an improvement in the shielding competency of the fabricated glasses. The highest interactions between photons and the atoms of the glasses occur around 0.122 MeV, and the glass samples have an excellent blocking capacity to photons, according to the effective atomic number (Zeff) data. Furthermore, the half value layer (HVL) revealed that when the BaO level in the composition increases, the HVL values will reduces. As a conclusion, the radiation shielding factors revealed that G7 glass with 30 mol% of BaO is the optimum performance of the produced samples.

Short-range structure, the role of bismuth and property-structure correlations in bismuth borate glasses.

Bismuth-containing borate glasses, xBi2O3-(1 - x)B2O3, were synthesized in the broad composition range 0.20 ≤ x ≤ 0.80 by melting in Pt crucibles and splat-quenching between two metal blocks. Infrared reflectance spectra, measured in the range 30-5000 cm-1, were transformed into absorption coefficient spectra and then deconvoluted into component bands to probe the glass structure as a function of composition. Integrated intensities of bands above 800 cm-1 were used in combination with mass and charge balance equations to quantify the short-range borate structure in terms of the molar fractions X4m, X4o, X3, X2, X1 and X0 for borate units BØ4-, BØ2O23-, BØ3, BØ2O-, BØO22- and BO33-, where Ø and O- denote bridging and non-bridging oxygen atoms. Borate tetrahedral units were found to be present in both the meta-borate, BØ4-, and ortho-borate, BØ2O23-, forms with BØ4- constituting the dominating tetrahedral species for 0.20 ≤ x ≤ 0.70. The BØ2O23- units prevail at higher Bi2O3 levels (x > 0.7), and coexist with their isomeric triangular borate species BO33- (BØ2O23- ⇌ BO33-). The present IR results for the total molar fraction of borate tetrahedral units, X4 = X4m + X4o, are in very good agreement with reported NMR results for the fraction of boron atoms in four-fold coordination, N4. Besides evaluating X4m and X4o, the present work reports also for the first time the fractions of all types of triangular borate species X3-n with n = 0, 1, 2 and 3. The IR region below 550 cm-1 was found to be dominated by the Bi-O vibrational activity in coexisting ionic (160-230 cm-1) and distorted BiO6 sites (330-365 cm-1 and 475-510 cm-1), a result reflecting the dual role of Bi2O3 as glass-modifier and glass-former oxide. The latter role dominates in glasses exceeding 60 mol% Bi2O3, and is consistent with the extended glass formation in the bismuth-borate system. The structural results were used to calculate the average number of bridging B-Ø bonds per boron center, the average Bi-O and B-O single bond energy, and the atomic packing density of the studied glasses. These properties vary approximately linearly with Bi2O3 content in the three regimes 0.2 ≤ x ≤ 0.4, 0.4 < x ≤ 0.6 and 0.6 < x ≤ 0.83, and contribute collectively to the composition dependence of glass transition temperature.

Nanometric Fluctuations of Sound Velocity in Alkali Borate Glasses and Fragility of Respective Melts

The network structure of borate glass is remarkably modified by the addition of alkali metals. The alkali metal dependences of the first sharp diffraction peak (FSDP) and the boson peak (BP) are investigated in alkali borate glasses by elastic and inelastic neutron scattering experiments. With an increase in ionic radius of alkali ions, both the width ΔQ of FSDP and the BP energy decrease. The comparison of the characteristic length of medium‐range order (MRO) predicted by the FSDP and the position of the BP allows us to find the mean‐square fluctuations of the transverse sound velocity within series of alkali borate glasses. It is shown that the fragility of the respective alkali borate melts inversely correlates with the mean‐square fluctuations of the transverse sound velocity in glassy state.

Constant Composition Groups in Glass of Sodium–Borate Systems According to the Data of X-Ray Diffractometry

X-ray spectra of glass of the sodium-borate system are obtained by the method of X-ray diffractometry. Using the proposed processing of these spectra, the smallest elements of the sodium–borate glass structure (constant stoichiometry groups, CSGs), which unambiguously determine their properties, are determined. The method for determining the smallest elements of the glass structure consists of comparing the glass contours with the known contour of a glass of a stoichiometric composition.

Mixed alkali effects in Er3+‐doped borate glasses: Influence on physical, mechanical, and photoluminescence properties

AbstractEngineering borate glass structure by simple compositional modification is essential to meet the particular demands from both industrial and photonic research communities. In this article, we demonstrate how the mixing of Li2O with Na2O, K2O, or Cs2O influences the relative abundance of 3‐ and 4‐coordinated borons in the glass network, as exhibited by nuclear magnetic resonance (NMR) and Raman spectra. A systematic study is given of the alkali mixing effect on the glass properties including: glass transition temperature, microhardness, density, refractive index, and particularly the near‐infrared photoluminescence properties (eg, bandwidth and lifetime) of Er3+ which has been barely studied in mixed alkali borate glasses. It is interesting to note that the glass transition temperature, refractive index and emission lifetime of Er3+ manifest mixed alkali effect, in sharp contrast with microhardness, density, and emission bandwidth which vary monotonically upon the alkali mixing. The possible causes for the differences are discussed in the light of the compositional dependence of boron species and nonbridging oxygen upon alkali mixing.

Statistical Mechanical Modeling of Borate Glass Structure and Topology: Prediction of Superstructural Units and Glass Transition Temperature.

Predicting the compositional evolution of the atomic-scale structure and properties of oxide glasses is important for designing new materials for advanced applications. A statistical mechanics-based approach has recently been applied to predict the composition-structure evolution in binary phosphate glasses, while topological constraint theory (TCT) has been applied in the last decade to predict the structure-property evolution in various oxide and nonoxide glass systems. In this work, we couple these two approaches to enable quantitative predictions of the compositional dependence of glass transition temperature and the population of superstructural units. The object of the study is the lithium borate glass system because they feature interesting structural characteristics (e.g., boron anomaly), and ample structure and property data are available. In these glasses, the average coordination number of boron first increases when lithium modifiers are added and then later decreases accompanied by network depolymerization. First, on the basis of 10B nuclear magnetic resonance spectroscopy data from literature, we present a statistical description of the structural evolution in lithium borate glasses by accounting for the relative enthalpic and entropic contributions to the bonding preferences. We show that the entire glass structure evolution (both short- and intermediate-range) can be predicted based on experimental structural information for only a few glass compositions. We then show that the developed structural model can be combined with a previously established TCT model to predict the compositional evolution of the glass transition temperature. This work thus opens a new avenue for the computational design of glasses with tailored properties.

Thermal and structural properties of Nd2O3-doped calcium boroaluminate glasses

Nd3+ doped CaO-Al2O-B2O3-CaF2 glasses were prepared by conventional melt-quenching technique, and their structural and thermal properties were studied. The amorphous nature of these samples was confirmed by X-ray diffraction (XRD). The measured density showed an increase with Nd2O3 doping, at the expense of CaO. Raman spectra presented changes with addition of Nd2O3, which indicated that the network structure of the glasses studied presented various borate groups, such as tetraborates, metaborates, ortho-borates and pyroborates units. The N4 values calculated from FTIR spectra revealed that incorporation of Nd2O3 into glass network converted the structural units from BO4 to BO3. From the analysis of DTA curves, we verified that Tg increased with the addition of Nd2O3; it was similar to the behavior caused by modifier oxides in the structure of borate glasses. Besides that, the calculated glass stability Tx–Tg for doped samples presented a decrease if compared to the undoped glass. Specific heat and thermal conductivity did not present significant changes with Nd2O3 concentration, up to 2.30 mol.%. The results of density, DTA, Raman and FTIR reinforced the idea that Nd2O3 acted as network modifier.

The effect of the addition of gallium on the structure of borate glass

The effect of the addition of gallium on the structure of borate glass

On the dual role of ZnO in zinc-borate glasses

ZnO incorporated borate glass structures have been produced by classical melt-quench technique. The effect of ZnO concentration on the behavior of ZnO in glass network as a modifier or network former has been clearly defined by combining various characterization tools. FT-IR transmittance spectra have been used to study the structure of glass systems. Temperature dependent electrical measurements have been performed to investigate the conduction mechanisms, especially at low temperatures. Activation energies determined by considering classical Arrhenius relation and small polaron hopping mechanism support the comments on the behavior of ZnO in glass network. Optical band gap and Urbach energy values have been calculated using optical measurements. Also, Spectroscopic Ellipsometry technique has been used to determine optical constants (refractive index and extinction coefficient) by Cauchy–Urbach model. Results showed that refractive index of borate glasses can be controlled by the composition of ZnO in the structure. Combining all of the outputs from different characterizations, it has been concluded that the amount of ZnO in borate glass structure has a dramatic effect on the number of non-bridging oxygen atoms that determines the role of ZnO as a modifier/network former. ZnO acted as a network former in samples having more than 5% (weight%) incorporation.

Structural and optical investigations of Eu3+ ions in lead containing alkali fluoroborate glasses

Lead containing alkali fluoroborate glasses (LAFB) with molar composition of 20PbO+5CaO+5ZnO+10AF+59B2O3+1Eu2O3 (where A=Li, Na and K) were prepared and investigated by the TG-DTA, FT-Raman, optical absorption, fluorescence and decay curve analysis. The influence of alkali content on the structure of borate glasses was investigated by FT-Raman spectroscopy. The thermal properties of the glasses have been studied by TG-DTA analysis. Judd–Ofelt intensity parameters are derived from the absorption spectra and also from the emission spectra under various constraints. The effect of thermalization on the oscillator strengths of the absorption transitions originating from the ground (7F0) and the first excited (7F1) states of Eu3+ ions have been discussed. The J–O intensity parameters obtained by applying thermal correction to 7F0→5D2 and 7F6 absorption oscillator strengths were used to calculate the various spectroscopic properties. The predicted values of radiative lifetime (τR) and luminescence intensity branching ratio (βR) are compared with the measured values for 5D0 level. The decay profiles were found to be single exponential in all the three glasses. The spectroscopic properties confirm the potentiality of present LAFB glasses doped with Eu3+ ions as laser host materials to produce an intense red luminescence at 612nm corresponding to 5D0→7F2 emission level and have significant importance in the development of emission rich optical systems.

The structure of borate glass

The existing hypotheses on the structure of alkali borate glass were comprehensively analyzed. Their imperfection in explaining the dependences of the properties of the glasses on their composition was noted. Alternative schemes of structural borate complexes which more convincingly explain the characteristics of the change in the properties of this glass are proposed.

Spatial distribution of lithium ions in glasses studied by 7Li{6Li} spin echo double resonance

This manuscript introduces 7Li{6Li} spin echo double resonance (SEDOR) spectroscopy as a novel approach for studying the spatial distribution of lithium ions in solid electrolytes. Theoretical simulations using density operator theory as well as experimental validation on the model compound lithium carbonate reveal that this method affords a selective measurement of 7Li-6Li heteronuclear dipole-dipole couplings. Dipolar second moments characterizing internuclear lithium-lithium interactions have been measured in lithium silicate (Li2O)(x)(SiO2)(1-x), (0.1 < or = x < or = 0.4) and lithium borate (Li2O)(x)(B2O3)(1-x), (0.1 < or = x < or = 0.3) glasses. The results indicate that the spatial distributions of the lithium ions in these two glass systems are decidedly different. In the lithium silicate glass system, the results give clear evidence of strong cation clustering for x < or = 0.3, providing quantitative support for a previously proposed model of a one-dimensional channel structure. In contrast, in the lithium borate glass system, the cations seem to be more or less randomly distributed. Nevertheless, an observed superlinear dependence of M2(7Li-6Li) as a function of ion concentration indicates subtle changes of the lithium arrangement principles, which are discussed in relation to the previously proposed ring structure of borate glasses.

Effect of heat treatment and concentration of Mn and Fe on the structure of borate glass

We have studied the magneto-optic Faraday effect (FE) and electron paramagnetic resonance (EPR) in an aluminum potassium borate glass containing Fe oxides as an impurity in a concentration of 1.5 mass % and Mn impurity in variable concentration from 0 to 1.2 mass %. When manganese oxide is added to the glass composition, the paramagnetic contribution to the Faraday effect increases more slowly than the change in the total concentration of paramagnetic ions, which allows us to hypothesize the appearance of clusters in which the paramagnetic ions are coupled by antiferromagnetic interactions. Formation of clusters upon addition of manganese oxide is confirmed by the change in the nature of the EPR spectra, where we observe a manganese concentration dependence of the distribution of iron atoms with respect to the different positions in the glass matrix. Heat treatment leads to a strong increase in the Faraday effect and a change in the spectral dependences of the Faraday effect and the EPR, which is explained by enlargement of the clusters and appearance of nanoparticles.

Dependence of sodium borate glass structure on depth from the sample surface

Structural properties of sodium borate glasses with nominal composition 0.3Na2O–0.7B2O3 were investigated as a function of depth from the sample surface by employing infrared specular reflectance spectroscopy. To this aim, cylindrical samples of 2mm in thickness were prepared from the same batch by quenching the melt into appropriate shapes and surface layers were subsequently removed by appropriate polishing. The analysis of the mid infrared spectra revealed the presence of boron–oxygen triangles, BØ3, BØ2O−, and tetrahedra, BØ4-, as the short-range order units building the glass network (Ø denotes an oxygen atom bridging two boron centers). It was found that the relative population of the BØ4- tetrahedral units increases with thickness of the removed layer, and this structural change was shown to affect also the distribution of network sites hosting the sodium ions. In particular, the spectral weight of the asymmetric far infrared absorption profile was found to increase gradually towards lower frequencies with thickness of the removed layer. These findings were discussed in terms of cooling rate gradients from the surface to the core of the glass sample.

Raman study on B 2O 3–CaO glasses

Glasses are of special interest nowadays mainly because of the large applications that they span. Raman spectroscopy is an experimental technique appropriate for providing information about the structure of local arrangements of the atoms in glasses. The influence of CaO content on the structure of borate glasses was investigated by Raman spectroscopy. At low calcium oxide content the structure of calcium borate glass consists mainly of boroxol groups and a smaller number of pentaborate groups. In the vitreous network there are few diborate groups, chain type metaborate groups and pyroborate groups. At high calcium oxide content, pentaborate, orthoborate and metaborate groups appear. The increase of calcium oxide content yields an increase in number of non-bridging oxygen ions. Therefore, we conclude that calcium ions act as network modifiers in borate glasses.