Field strength effect on structure,hardness, and crack resistance in single modifier aluminoborosilicate glasses

Although the interactions among glass formers and modifiers, for example, connectivity and charge distribution, have been studied extensively in oxide glasses, the impact of a particular modifier species on the mechanical performance of aluminoborosilicate (ABS) glasses is not well understood. This work compares the indentation properties of six ABS glasses, each of which contains a different network modifier (NWM) with varying field strength (FS). Three alkali and three alkaline earth ABS glasses were designed with low NWM content and [NWM] ≈ [Al₂O₃], to test the modifier FS effect at low concentrations and to maximize three-coordinated boron. It has been found that both hardness and crack resistance increase with increasing FS in these ABS systems, which is surprising in the context of historical reports. Using ¹¹B, ²⁷Al, and ²⁹Si solid-state nuclear magnetic resonance, this work provides evidence of how charge distributions differ as a function of NWM species, and how this relates to the observed indentation behaviors.     

Field strength effect on elastoplastic behavior of aluminoborosilicate glass: II. Volumetric recovery

The field strength (FS) effect of six different network modifiers on the elastoplastic properties of aluminoborosilicate glasses was explored using a volumetric recovery study. This work, in conjunction with Part I, explored the intersection of hardness, crack resistance, and other physical properties with glass elasticity. Results showed that (1) the elastic volume fraction decreased with FS for both the alkali and alkaline earth (AE) glasses; (2) the Poisson's ratio did not trend with pile-up or shear flow volume fraction; (3) the elastic-to-plastic deformation ratio increased with applied load and decreased with modifier FS for both the alkali and AE glasses; and (4) an increase in plasticity correlated with increased hardness, crack resistance, and elastic moduli.     

Crystallization,spectroscopic and dielectric properties of CuO-added magnesium aluminosilicate-based glasses

In this work, CuO-doped MgO-Al₂O₃-SiO₂ based glasses have been synthesized successfully through conventional melt quenching method, and the effect of CuO content on the structure and properties of the glasses was investigated. The results revealed that CuO could act as a glass modifier to depolymerize the silicate network and its effect was superior to that of MgO. In addition, the main crystalline phase was α-cordierite (Mg₂Al₄Si₅O₁₈), indicating that copper ions did not participate in the formation of the crystalline phase, and still existed in the interstitial position. The characteristic absorption band around 750 nm owing to the ²B_1g→²B_2g transition of Cu²⁺ ions appeared on the optical transmittance spectra, which confirmed the existence of Cu²⁺ ions in the tetragonally distorted octahedral sites. The luminescence center was caused by Cu⁺ ions, and the luminescence lifetime decreased with the addition of CuO. The dielectric constant and dielectric loss increased with the increase of CuO content, indicating an increase in the insulation performance. Finally, the obtained chromaticity coordinate parameters indicate that the prepared CuO-doped magnesium aluminosilicate-based glasses can be applied in optical and electrical fields.     

ON THE DETERMINATION OF THE CONSTITUTION OF GLASSES1

This method of determination of the constituents of glasses is entirely new in its way. It is derived from the author's experiments on the causes of the surface devitrify-cation of glasses. It is quite natural to produce crystals in glasses when heated several times at high temperatures. The glasses are super cooled liquids and are very viscous at low temperatures. But, when they are heated at higher temperatures, they attain low viscosities to produce crystals in them. In general, the chemical composition of the crystals produced (primary phase) in ordinary glasses without B₂O₂ is SiO₂. And for production of an elementary body of crystals of silica, there should be at least three neighboring molecules of silica moving within some ranges of speed. The motion of such molecules in glasses is set by two causes: the one is that quantity of energy given to the molecules by heating, and the other is that lowering of viscosity of the medium by heating. Heating glasses to certain temperatures is the exclusive cause of the crystal production of glasses. This has been already explained by many persons and no ambiguity has been left unsolved. The author has given another important cause for crystal production on glass surfaces and has described the interpretation. ³ 1 Received August 11, 1926.
From these views, the author has arbitrarily defined devitrify-cation in five degrees. They are seen in accompanying photographs. It has been determined that these degrees of devitrify-cation were entirely coincident with the quantities of dissolved silica in glasses. The experiments have been conducted for a series of glasses of alkali silicates and alkali lead silicates. From the results of these experiments, the author has determined the constitutions of those silicates in glasses to be meta-disilicates and the double compounds to consist of those meta-disilicates. As the result of the determination of the constituents of alkali silicates and of alkali lead silicate glasses, it is pointed out that the compositions of crucibles to melt glasses of different silica content, should be either rich Al₂O₃: or rich SiO₂ according to the dissolving power of glasses for silica.     

Degree of Polymerization of Aluminosilicate Glasses and Melts

This paper presents the results of analyzing the data available in the literature on the structure and properties of silicate glasses and melts that contain Ti⁴⁺, Al³⁺, and Fe³⁺ cations in addition to alkali and alkaline-earth cations. It is established that the aforementioned multivalent cations in glasses and melts have a coordination number of four and play the role of network-formers. Aluminosilicate glasses and melts with the mole fraction ratio Al₂O₃/M ₂(M)O = 1 are of special interest. For these glasses, the structure is considered to be completely polymerized and, contrary to traditional concepts, their properties depend on the concentration ratio Al₂O₃/SiO₂. Taking into account that the structure of aluminosilicate glasses involves unusual structural units (such as triclusters) and a certain number of nonbridging oxygen atoms, a formula is proposed for calculating the degree of polymerization. The proposed formula is used to calculate the degree of polymerization for a number of Na₂O · Al₂O₃ · mSiO₂ glasses and the CaO · Al₂O₃ · 2SiO₂ glass. It is demonstrated that the calculated degrees of polymerization correlate with the experimentally measured viscosities of the relevant melts.     

Structure-property relations in crack-resistant alkaline-earth aluminoborosilicate glasses studied by solid state NMR

The effect of the average ionic potential ξ = Ze/r of the network modifier cations on crack initiation resistance (CR) and Young's modulus E has been measured for a series of alkaline-earth aluminoborosilicate glasses with the compositions 60SiO₂–10Al₂O₃–10B₂O₃–(20−x)M₍₂₎O–xM’O (0 ≤ x ≤ 20; M, M’ = Mg, Ca, Sr, Ba, Na). Systematic trends indicating an increase of CR with increasing ionic potential, ξ, have been correlated with structural properties deduced from the NMR interaction parameters in ²⁹Si, ²⁷Al, ²³Na, and ¹¹B solid state NMR. ²⁷Al NMR spectra indicate that the aluminum atoms in these glasses are essentially all four-coordinated, however, the average quadrupolar coupling constant <C_Q> extracted from lineshape analysis increases linearly with increasing average ion potential computed from the cation composition. A similar linear correlation is observed for the average ²⁹Si chemical shift, whereas the fraction of four-coordinate boron decreases linearly with increasing ξ. Altogether the results indicate that in pure alkaline-earth boroaluminosilicate glasses the crack resistance/E-modulus trade-off can be tailored by the alkaline-earth oxide inventory. In contrast, the situation looks more complicated in glasses containing both Na₂O and the alkaline-earth oxides MgO, CaO, SrO, and BaO. For 60SiO₂–10Al₂O₃–10B₂O₃–10MgO–10Na₂O glass, the NMR parameters, interpreted in the context of their correlations with ionic potentials, are consistent with a partial network former role of the MgO component, enhancing crack resistance. Altogether the presence of MgO in aluminoborosilicate glasses helps overcome the trade-off issue between high crack resistance and high elasticity modulus present in borosilicate glasses, thereby offering additional opportunities for the design of glasses that are both very rigid and very crack resistant.     

Chemical durability of borosilicate pharmaceutical glasses: Mixed alkaline earth effect with varying [MgO]/[CaO] ratio

Glass for pharmaceutical packaging requires high chemical durability for the safe storage and distribution of newly developed medicines. In borosilicate pharmaceutical glasses which typically contain a mixture of different modifier ions (alkali or alkaline earth), the dependence of the chemical durability on alkaline earth oxide concentrations is not well understood. Here, we have designed a series of borosilicate glasses with systematic substitutions of CaO with MgO while keeping their total concentrations at 13 mol% and a fixed Na₂O concentration of 12.7 mol%. We used these glasses to investigate the influence of R = [MgO]/([MgO] + [CaO]) on the resistance to aqueous corrosion at 80°C for 40 days. It was found that this type of borosilicate glass undergoes both leaching of modifier ions through an ion exchange process and etching of the glass network, leading to dissolution of the glass surface. Based on the concentration analysis of the Si and B species dissolved into the solution phase, the dissolved layer thickness was found to increase from ~100 to ~170 nm as R increases from 0 to 1. The depth profiling analysis of the glasses retrieved from the solution showed that the concentration of modifier ions (Na⁺, Ca²⁺, and Mg²⁺) at the interface between the solution and the corroded glass surface decreased to around 40%–60% of the corresponding bulk concentrations, regardless of R and the leaching of modifier cations resulted in a silica-rich layer in the surface. The leaching of Ca²⁺ and Mg²⁺ ions occurred within ~50 and <25 nm, respectively, from the glass surface and this thickness was not a strong function of R. The leaching of Na⁺ ions varied monotonically; the thickness of the Na⁺ depletion layer increased from ~100 nm at R = 0 to ~200 nm at R = 1. Vibrational spectroscopy analysis suggested that the partial depletion of the ions may have caused some degree of the network re-arrangement or re-polymerization in the corroded layer. Overall, these results suggested that for the borosilicate glass, replacing [CaO] with [MgO] deteriorates the chemical durability in aqueous solution.     

An ultrasonic study on ternary xPbO–(45-x)CuO–55B2O3 glasses

A series of xPbO–(45-x)CuO–55B₂O₃ glasses (5 ≤ x ≥ 40 mol %) were prepared by the melt-quenching technique. The X-ray diffraction (XRD) patterns of the prepared glasses are found to have amorphous structure. An extensive ultrasonic study has been made to explore the structural role of PbO and CuO in the borate network. Various elastic properties were calculated from the measured data of density and ultrasonic velocity. Ultrasonic velocity and elastic moduli revealed broad humps at about 20 mol % PbO, which are attributed to the borate anomaly. Below 20 mol % PbO, all Pb²⁺ ions are considered to be entering the borate network as a glass modifier. This results in the transforms the borate network from an open structure to a denser three-dimensional structure due to BO₃ → BO₄ conversion. Beyond 20 mol, addition of PbO results in the formation of metaborate, pyroborate, and orthoborate units with NBOs. This weakness the glass structure and decrease both ultrasonic velocity and elastic moduli. The elastic properties were predicted and quantitatively analyzed by taking into account the effect of boron coordination number on the compositional and structural parameters involved in Makishima–Mackenzie's theory, ring deformation model and bond compression model. An excellent agreement between the computed theoretical and experimental elastic moduli, micro-harness and Poisson's ratio was achieved for majority of samples.     

Structural dependence of chemical durability in modified aluminoborate glasses

Alkali and alkaline earth aluminoborate glasses feature high resistance to cracking under sharp contact loading compared to other oxide glasses. However, due to the high content of hygroscopic B₂O₃, it is expected that applications of these glasses could be hindered by poor chemical durability in aqueous solutions. Indeed, the compositional and structural dependence of their dissolution kinetics remains unexplored. In this work, we correlate the dissolution rates of aluminoborate glasses in acidic, neutral, and basic solutions with the structural changes induced by varying the aluminum-to-boron ratio. In detail, we investigate a total of seventeen magnesium, lithium, and sodium aluminoborate glasses with fixed modifier content of 25 mol%. We show that the structural changes induced by alumina depend on the network modifier. We also demonstrate a correlation between the chemical durability at various pH values and the structural changes in Mg-, Li- and Na-aluminoborate glasses. The substitution of alumina by boron oxide leads to a general decrease in chemical corrosion in neutral and acidic solutions. The lowest dissolution rate value is observed in Mg-aluminoborate glasses, as a consequence of the intermediate character of magnesium which can increase the network cross-linking. For basic solutions, the chemical durability is almost constant for the different amount of alumina in the three series, likely because B₂O₃ is susceptible to nucleophilic attack, which is favored in high-OH⁻ solutions.     

Influence of Al2O3/SiO2 ratio in multicomponent LNAS glasses and glass-ceramics on the crystallization behavior,microstructure and mechanical performance

Transparent glass-ceramics containing eucryptite and nepheline crystalline phases were prepared from alkali (Li, Na) aluminosilicate glasses with various mole substitutions of Al₂O₃ for SiO₂. The relationships between glass network structure and crystallization behavior of Li₂O–Na₂O–Al₂O₃–SiO₂ (LNAS) glasses were investigated. It was found that the crystallization of the eucryptite and nepheline in LNAS glasses significantly depended on the concentration of Al₂O₃. LNAS glasses with the addition of Al₂O₃ from 16 to 18 mol% exhibited increasing Q⁴ (mAl) structural units confirmed by NMR and Raman spectroscopy, which promoted the formation of eucryptite and nepheline crystalline phases. With the Al₂O₃ content increasing to 19–20 mol%, the formation of highly disordered (Li, Na)₃PO₄ phase which can serve as nucleation sites was inhibited and the crystallization mechanism of glass became surface crystallization. Glass-ceramics containing 18 mol% Al₂O₃ showed high transparency ～84% at 550 nm. Moreover, the microhardness, elastic modulus and fracture toughness are 8.56 GPa, 95.7 GPa and 0.78 MPa m^1/2 respectively. The transparent glass-ceramics with good mechanical properties show high potential in the applications of protective cover of displays.     

THE COMPOSITION OF BARIUM GLASS1

In this paper the relation between the composition of barium glasses and the optical constants is discussed as well as the general rules for proportioning batches. The important results and conclusions are given by the figures. After the required amounts of BaO and B₂O₃ have been obtained from figures 2 and 3, the amount of SiO₂ can be obtained from figure 5, the alkali and ZnO from figure 7 and the Al₂O₃ from figure 8. If the total exceeds 100, the ZnO and the Al₂O₃ may be reduced. The proportions cannot be as definitely expressed as in the case of lead glasses and more experience is required to enable one to change the optical properties at will.     

Competitive effects of free volume,rigidity, and self-adaptivity on indentation response of silicoaluminoborate glasses

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 SiO₂ to a 25Li₂O–20Al₂O₃–55B₂O₃ glass 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 Al₂O₃ and/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 SiO₂ addition. 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.     

Cation Field Strength Effects on Boron Coordination in Binary Borate Glasses

The field strength of modifier cations in boron‐containing oxide glasses has important but complex effects on boron coordination, and has long been known to have major effects on glass and liquid properties. With well‐constrained compositional and fictive temperature information in three binary borate glass series, we report how different modifier cations (Na⁺, Ba²⁺, Ca²⁺) affect boron coordination (¹¹B MAS NMR), as well as glass transition temperatures and configurational heat capacities (DSC). Using estimated reaction enthalpies for converting a ^[4]B to a ^[3]B with an NBO from previous studies, we compare boron coordinations in glasses with different modifier cations on an isothermal basis. Temperature and modifier cation effects can thus be isolated. At low modifier contents [R = (Na₂,Ca,Ba)O/B₂O₃<0.45], N₄ is systematically higher in the order Na>Ba>Ca, suggesting the enhanced stabilization of NBO for the divalent cations, especially for the smaller Ca²⁺. At higher R values, N₄ for Na borates drops below values for Ca and Ba borates. The trend in N₄ with modifier field strength reverses at high R values (~ R > 0.7), with Ca > Ba > Na. The transition may be related to the enhanced stabilization of ^[4]B‐O‐^[4]B groups by higher field strength cations in NBO‐rich glasses in which boron is the primary network component.     

A closer-look on Copper(II) oxide reinforced Calcium-Borate glasses: Fabrication and multiple experimental assessment on optical,structural, physical,and experimental neutron/gamma shielding properties

This study aimed to fabricate six different Copper(II) oxide reinforced Calcium-Borate glasses with different types of substitutions such as Al₂O₃/V2O₅, BaO₂/V₂O₅, and ZnO/V₂O_5. Accordingly, a depth characterization process has been performed for ACV, BCV and ZCV glasses with a nominal composition of 55B₂O₃–35CaO–9Al₂O₃-0.5CuO-0.5V₂O₅, 55B₂O₃–35CaO-8.5Al₂O₃-0.5CuO–1V₂O₅, 55B₂O₃–35CaO–9BaO₂-0.5CuO-0.5V₂O₅, 55B₂O₃–35CaO-8.5BaO₂-0.5CuO–1V2O5, 55B2O3–35CaO–9ZnO-0.5CuO-0.5V2O5, 55B2O3–35CaO-8.5ZnO-0.5CuO–1V₂O₅. Optical, structural, physical, and experimental neutron/gamma shielding properties of synthesized glasses were determined, respectively. Experiments measuring neutron exposure indicated how well glass samples attenuated fast neutrons. The RADACS software was used to record data from a BF3 gas proportional detector from the Canberra NP-100B series and a 241Am/Be neutron source with a 10 mCi activity. The absorption edge belonging to the samples are found between 420 nm and 480 nm. Our findings showed that the optical band gaps for the samples ranged from 1.179 to 2.022 eV. The wavenumber range of 400–1600 cm^-1 was evaluated for the resulting peaks. The region with the highest band formation was approximately 760–1170 cm^-1. While BCV0.5 and BCV1 glasses with 9% and 8.5% BaO₂ insertion have the largest MAC values ranging between 2.255–0.076 and 2.156–0.076 cm²/g, the lowest MAC values varying between 0.361–0.0761 and 0.366–0.076 cm²/g belong to ACV0.5 and ACV1 glasses with 9% and 8.5% Al₂O₃ addition. Our results showed that the BCV glass family has superior material properties among the fabricated glasses. It can be concluded that BaO₂/V₂O₅ glasses may be used in replacement of Copper(II) oxide glasses to provide monotonic behavior on crucial characteristics while maintaining the greatest density increase for large gamma ray shielding properties.     

Structure and crystallization behavior of complex mold flux glasses in the system CaO-Na2O-Li2O-CaF2-B2O3-SiO2: A multi-nuclear NMR spectroscopic study

The structure of mold flux glasses in the system CaO-(Na,Li)₂O-SiO₂-CaF₂ with unusually high modifier contents, stabilized by the addition of ∼4 mol% B₂O₃, is studied using ⁷Li, ²³Na, ¹⁹F, ¹¹B, and ²⁹Si magic-angle-spinning (MAS), and ⁷Li{¹⁹F} and ²³Na{¹⁹F} rotational echo double-resonance (REDOR) nuclear magnetic resonance (NMR) spectroscopy. When taken together, the spectroscopic results indicate that the structure of these glasses consists primarily of dimeric [Si₂O₇]⁻⁶ units that are linked to the (Ca,Na,Li)-O coordination polyhedra, and are interspersed with chains of corner-shared BO₃ units. The F atoms in the structure are exclusively bonded to Ca atoms, forming Ca(O,F)_n coordination polyhedra. This structural scenario is shown to be consistent with the crystallization of cuspidine (3CaO·2SiO₂·CaF₂) from the parent melts on slow supercooling. The progressive addition of Li to a Na-containing base composition results in a corresponding increase in the undercooling required for the nucleation of cuspidine in the melt, which is attributed to the frustrated local structure caused by the mixing of alkali ions.     

On the anode effect in cryolite-alumina melts—II the initiation of the anode effect

Polarization curves obtained with graphite anodes in cryolite-alumina melts by steady state, potential sweep and galvanostatic measurements exhibited three steps at low alumina concentrations, due to the formation of CO₂ and CF₄, prior to the anode effect (AE), and probably of F₂ after the occurrence of the AE. Formation of CF₄ started at ~2·8 V positive to the aluminum electrode, while the potential and the critical current density (ccd) at which the AE occurred were 3·5 V and 0·11 A/cm² resp. in purified cryolite and 2·7 V and 2·1 A/cm² at 1 wt per cent Al₂O₃. The proportion of CF₄ in the gas reached 40 per cent in purified melts, but decreased sharply on the addition of alumina. At > 2 wt per cent Al₂O₃ the ccd decreased when the external pressure was lowered approximately in proportion to the volume of escaping gas. It is concluded that the AE occurs when the melt adjacent to the anode is depleted with respect to oxygen-containing ions, and the rate of fluoride ion discharge exceeds the rate of CF₄ formation.     

Seeded Stage III glass dissolution behavior of a statistically designed glass matrix

The dissolution rate of some glasses accelerates after prolonged time spent at a slow, residual dissolution rate. This phenomenon is referred to as Stage III behavior. The acceleration in glass dissolution rate linked to Stage III behavior is significant and may be the most impactful behavior to long-term performance of glass in a repository. This work is aimed at understanding the effect of glass composition on Stage III behavior to add a level of technical defensibility to glass disposal. To this end, a set of 24 glass compositions were statistically designed, where eight glass components (SiO₂, B₂O₃, Al₂O₃, CaO, Na₂O, SnO₂, ZrO₂, and Others) have been independently varied in order to study the individual effects of each glass component. These glasses have been subjected to static dissolution tests at 90°C in deionized water and then seeded with zeolite Na-P2 28 days into the testing to induce Stage III behavior. The response of the glasses to the zeolite seeds fell into four primary types: (1) no response to seeds; (2) an immediate linear sustained acceleration in the rate; (3) an immediate linear acceleration in the rate followed by a decrease; and (4) a progressive acceleration in the rate that is concurrent with the addition of the seeds. The main glass components observed to influence these behaviors were CaO, Al₂O₃, B₂O₃, and ZrO₂, where (1) CaO influenced which glasses showed a Stage III response to seeds (high CaO: types 2, 3, and 4) or did not respond to seeds (low CaO: type 1), (2) Al₂O₃ and B₂O₃ influenced which glasses showed a sustainable Stage III response (high Al₂O₃: types 2 and 4) versus transitory response (low Al₂O₃ and high B₂O₃: type 3), and (3) ZrO₂ concentration influenced whether glasses showed a linear (high ZrO₂: type 2) versus progressive (low ZrO₂: type 4) response to seeds.     

Luminescence of modified nonbridging oxygen hole centers in silica and alkali silicate glasses

This paper reports on the results of the investigation of the cathodoluminescence spectra of silica and alkali silicate glasses upon excitation with a pulsed electron beam (energy, 180 keV; current density, 700 A/cm²; pulse duration, 2 ns). The luminescence band observed in the energy range 2.4–2.6 eV is assigned to modified structural defects of the ≡Si-O·/Me ⁺ type. These defects are revealed under high-density electronic excitation and, unlike the known L centers in alkali silicate glasses, are interpreted as a variety of nonbridging oxygen hole centers (defects of the dangling bond type) subjected to a disturbing action of the nearest neighbor alkali metal cations. The cathodoluminescence of similar centers is observed in neutron-irradiated silica glasses with lithium impurities; alkali silicate glasses with Li, Na, and K cations; and glasses in the two-alkali Na-K systems. It is established that the energy of the radiative transition of a modified nonbridging oxygen hole center, namely, ≡Si-O·/Me ⁺, depends on the alkali cation type.     

Mixed modifier effect in lithium‐calcium borosilicate glasses

The mixed modifier effect (MME) in the lithium‐calcium borosilicate glasses, which have a composition of 0.4[(1?x)Li₂O–xCaO]–0.6[(1?y)B₂O₃–ySiO₂] with x in the range of 0~1 and y in the range of 0.33~0.83, is investigated. The MME manifests itself as a positive deviation from linearity in the activation energy of electrical conductivity (Ea^σ) and as a negative deviation from linearity in the fraction of four‐coordinated boron (N₄), glass transition temperature (T_g), dilatometric softening temperature (T_d), Vickers microhardness (H_v), dielectric constant (ε), and dielectric loss (tanδ). Moreover, the deviation, which exhibits a maximum at [CaO]/([CaO]+[Li₂O])=0.5, is enhanced with increasing [SiO₂]/[B₂O₃] ratio in the glass network. The observed MME in T_g, T_d, and H_v are attributed to the bond weakening in the network; however, the MME in ε, tanδ, and Ea^σ are caused by the obstruction of modifier transport in the glass network.     

Absorption and emission spectra of Eu3 doped Fluoroborate glasses

This paper reports the preparation of certain newly developed Eu³⁺ - doped fluoroborate glasses with H₃BO₃ and Na₂CO₃ as the network formers (NWF) and the fluorides of alkali (Na or Li) as the network intermediates (NWL). Further, by adding AIF₃ to the fluoroborate glasses, properties such as glass transparency; hardness; resistivity towards moisture and IR-transmission ability were found improved significantly. Under a UV source, these colourless Eu³⁺ - glasses did reveal brighter red emission. Compositional effects on the absorption and photoluminescence spectra of Eu: fluoroborate glasses were examined from their measured spectrophotometric profiles.