Glass Formation and Properties of Glasses in the PbO–ZnO–B2O3System

Glasses in the PbO–ZnO–B₂O₃system with a lead oxide content of less than 65 mol % are studied. The glass formation region for these glasses is determined. Their crystallization ability, density, and moisture resistance and the thermal, optical, and electrical properties are investigated. The composition–property curves are constructed. It is found that these dependences exhibit anomalies for glasses along the composition joins with constant boron oxide contents of 40 and 50 mol %. These anomalies can be associated with the change in the role of lead ions in the glass structure.     

High niobium oxide content in germanate glasses: Thermal,structural, and optical properties

Niobium alkali germanate glasses were synthesized by the melt‐quenching technique. The ternary system (90‐x)GeO₂–xNb₂O₅–10K₂O forms homogeneous glasses with x ranging from 0 to 20 mol%. Samples were investigated by DSC and XRD analysis, FTIR and Raman spectroscopy, and optical absorption. Structural and physical features are discussed in terms of Nb₂O₅ content. The niobium content increase in the glass network strongly modifies the thermal, structural and optical properties of alkali germanate glasses. DSC, Raman and FTIR analysis suggest niobium addition promotes NbO₆ groups insertion close to GeO₄ units of the glass network. XRD analysis also pointed out that samples containing high niobium oxide contents exhibit preferential niobium oxide‐rich phase after crystallization after heat treatment, which is similar to orthorhombic Nb₂O₅. Absorption spectra revealed high transmission range between 400 nm to 6.2 μm, added to a considerably decreased hydroxyl group content as the addition of niobium in the alkali germanate network. The niobium oxide‐rich phase crystallization process was studied and activation energy was determined, as well as nucleation and crystal growth temperatures and time for obtaining transparent glass‐ceramics.     

Bismuth and lead oxides codoped boron phosphate glasses for Faraday rotators

New magneto-optical vitreous materials were obtained by melting-quenching technique comprising wet route raw materials preparation. The glass has the following composition in oxide mol. %: 10 Li₂O, 9 Al₂O₃, 5 ZnO, (35; 20; 50) B₂O₃, (35; 50; 20) P₂O₅, 3 Bi₂O₃, 3 PbO, phosphorus and boron oxide being the vitreous network formers. It was also prepared a similar reference glass composition but without Bi₂O₃ and PbO. Optical and structural characterization by ultraviolet-visible (UV–Vis), Fourier Transform Infrared (FTIR) and Raman Spectroscopy of the bulk glasses showed a transmission over 90%, metaphosphate structure of glass together with Q² boron oxide units and P–O?B bonds. The mechanical parameters, hardness (H), Young's modulus (E) and fracture toughness (K_IC) of boron phosphate glasses, evaluated by micro- and nanoindentation techniques, demonstrated mostly higher values in comparison with those for alumino-phosphate glasses due to mixed boro-phosphate network. Thermal behavior was investigated by Differential Scanning Calorimetry (DSC) putting in evidence the vitreous transition temperature which decreases with about 45 °C when Bi and Pb oxides were added and two crystallization effects. The diamagnetic character of a highly transparent Bi and Pb oxide co-doped boron phosphate glass was confirmed by ellipsometry, and the glass presented high magneto-optical properties at the top of the commercial bulk products.     

Study of the properties of bismuth-borate systems toward low-melting lead-free glasses

Data on glass formation, crystallization, and physicochemical properties in the binary (Bi₂O₃-B₂O₃) and ternary (PbO-Bi₂O₃-B₂O₃, ZnO-Bi₂O₃-B₂O₃, and BaO-Bi₂O₃-B₂O₃) systems are presented. The feasibility of glasses with high bismuth oxide content (>80 mol %) is addressed. The formation of a glass network of octahedral [BiO₆] structural units rather than [BiO₃] ones in such systems is shown.     

Enhancement of UV laser-induced damage resistance of the fluoride-containing phosphate glasses by regulating the intrinsic defects

Low fluorine content containing fluorophosphate glasses have promising potential as ultraviolet (UV) optics to be used in high-energy laser systems. Systematic studies on the iron-doped and iron-free fluoride-containing phosphate glasses that were prepared at high and low melting temperatures explore the underlying interrelationship among the glass preparation conditions, intrinsic defects in produced glasses, and the anti-laser-damage properties. For the iron-doped fundamental frequency (1ω) absorptive glass, melting at high-temperature (1200°C) can reduce the extrinsic “impurity” concentration of Fe³⁺ ions, resulting in tiny increase of optical bandgap (by 1.6%) but significant reduce of the absorption coefficient by 34% at 355 nm. However, only tiny increase of the laser-induced damage threshold (LIDT) was achieved. For the iron-free third harmonic frequency (3ω) transparent glass, low-temperature (1000°C) melting process significantly reduced the absorptive intrinsic defects content of PO₃-EC, PO₄-EC, and phosphorous oxygen-bonded hole center defects, which made the UV absorption edge blue-shifted by 50 nm and the optical bandgap increased by ∼18%. The UV (355 nm) LIDT was significantly enhanced by ∼27%. Much lower absorption coefficient and larger bandgap of the iron-free glass relative to the iron-doped one endow it with larger a LIDT. In short, optimizing the glass melting temperature is a feasible method to enhance the UV laser-induced damage resistance of the fluoride-containing phosphate glasses through controlling the content of the extrinsic or intrinsic defects in produced glasses. The general routine is to achieve both the lower UV absorptive defect concentration (i.e., lower UV absorption at 355 nm) and the lower non-bridged oxygen ratio (i.e., denser glass network), as well as a larger optical bandgap (i.e., reduced probability of avalanche ionization breakdown), which together contribute to the enhancement of the anti-laser-damage performance of the investigated fluoride-containing phosphate glasses.     

Optical,Spectral, and Radiation-Shielding Properties of High-Lead Phosphate Glasses

The spectral, optical, physicochemical, radiative, and radiation-shielding properties of glasses in the PbO-P₂O₅-R _m O _n system (where R _m O _n stands for Group I–V element oxides) are investigated as a function of their composition. The composition of a colorless radiation-resistant high-lead glass suitable for production on a semicommercial scale is determined. The properties and optical quality parameters of the glass are studied. The new phosphate glass is a lead metaphosphate containing aluminum, alkali, and alkaline-earth oxides. This glass is resistant to radiation at doses up to 10⁷ R and has an optical transmission edge at 360 nm. The coefficient of absorption of gamma radiation for the new glass is larger than those of dense silicate flints. According to the optical parameters, the new glass lies between dense flints and dense barium flints in the Abbe diagram and compensates for the absence of the latter flints in catalogues of radiation-resistant glasses.     

Structural and thermal influence of niobia in aluminoborosilicate glasses

The addition of small amounts of niobia (Nb₂O₅) in borosilicate glasses was explored. By analysis on thermal and structural changes, we found evidences that niobium integrates the glass structure in octahedral NbO₆ coordination. Adding up to 8.0 mol% of Nb₂O₅, the oxide partially ruptured the glass structure, interfering in the BO₃/BO₄ ratio, but the predominant network configuration was maintained. Thermally, there was an increase in the processing interval and the glasses became more resistant against crystallization, with the presence of niobia. Also, the oxide contributed to a notable decrease in the viscosity of the melts. The improvement of such properties were obtained by the controlled dispersion of the oxide in the glass network structure, avoiding large areas of phase-to-phase separation to preserve the desired ability of these glasses to incorporate a wide range of elements.     

Reduction of crystallization ability of sodium zinc phosphate glass under X-ray radiation

The effect of X-ray radiation on the crystallization ability of maximally homogenized sodium zinc phosphate glass with a minimal light scattering value of V _v = 4 × 10^?6 cm^?1 has been investigated. The crystallization kinetics of the sodium zinc phosphate glass of the 33.9P₂O₅ · 56.6ZnO · 9.5Na₂O (mol % from analysis) composition under the conditions of homogeneous nucleation and X-ray radiation have been studied. It has been demonstrated that the crystallization properties of phosphate glasses are more sensitive to the synthesis method than those of silicate glasses. It has been established that sodium zinc phosphate glass crystals represent the main crystalline phase precipitated in the glass of the above composition. The main parameters of nucleation have been determined in glass without preliminary radiation, including stationary nucleation rate I _st, nonstationary nucleation time ??, and nucleation activation energy E _??. It have been found that the effect of the CuK _?? X-ray radiation leads to the slowing down or even cessation of the nucleation of crystals in glass (the result depends on the change in the radiation intensity along the sample depth) in the case when radiation takes place immediately during the nucleation thermal treatment of the sample in a high-temperature chamber of the X-ray device. The kinetics of sodium zinc phosphate crystallization in the samples upon their pretreatment by CuK _?? X-ray irradiation has been investigated. It has been shown that the rate of crystal nucleation in glasses exposed to X-ray radiation is lower than that in glasses without preliminary irradiation.     

Glass Formation in the ZrF4–LaF3–BaF2–NaF System

The glass formation in the ternary ZrF₄–LaF₃–BaF₂and quaternary ZrF₄–LaF₃–BaF₂–NaF systems at a zirconium fluoride content of 50–60 mol % is investigated. The glass formation region in the ternary system has the shape of a petal and lies along the LaF₃–BaZr₂F₁₀join. The glass formation regions in the quaternary system are either localized or continuous depending on the zirconium fluoride content. The glass transition temperatures T _gfall in the range 180–290°C, and the temperatures of the onset of crystallization lie in the range 250–340°C. Glasses crystallize in one, two, or three stages. The melting temperature varies in the range from 390 to 650°C. The microhardness of glasses is measured. The compositions of the most stable glasses are determined.     

Characterisation of glasses in the TeO2–WO3–PbO system

As potential candidates for photonic devices, non-linear materials and coatings, 22 glasses in the TeO₂–WO₃–PbO system have been formulated and prepared by conventional melting at temperatures ranging between 710 and 750 °C. The glass forming area has been determined for a wide region of the corresponding ternary diagram. Structural characterisation of the glasses was conducted through FTIR spectrometry and the variation of density values, which allowed calculation of the glass molar volume and the oxygen molar volume. UV–VIS spectra were recorded to determine optical absorption/transmission and energy gap values. Likewise, such results were correlated with the glasses composition and their ability for optical materials. DTA curves yielded data of transition temperature (T_g), onset crystallisation temperature (T_c) and the thermal stability range of glasses. Crystalline phases formed in devitrified and partially devitrified glasses were detected by X-ray diffraction. The properties and structural features of glasses were discussed in terms of their relative proportion of former/modifier oxides. The main glass former oxide is TeO₂, which arranges [TeO₄] groups with tetrahedral coordination, while PbO plays as glass modifier oxide. Tungsten oxide is incorporated as network former, alternating with TeO₂ and forming mixed linkages Te–O–W and W–O–W. WO₃ is the component that contributes most to increase the glass transition temperature, and to decrease both the oxygen molar volume and the thermal expansion coefficient.     

Hydrolytic resistance of K2O–PbO–SiO2 glasses in aqueous and high-humidity environments

Some historical glasses (lead-wood ash glasses, lead-crystal glasses…) are silicate glasses with high content of lead and potassium. This work presents the evaluation of the chemical stability of high-lead glasses in a high relative humidity atmosphere and as result of aqueous immersion. In both situations, the alteration mechanism begins with the lixiviation of alkali metal and lead ions, followed by the hydrolytic attack of the silica glass network. According to the results, the glasses with a higher content of lead show the fastest degradation due to their higher hygroscopicity. Environmental CO₂ can be dissolved in the adsorbed water and favor the formation of intermediate degradation compounds.     

Quantitatively predicting the optical and spectroscopic properties of Nd3+-doped laser glasses

Predicting the properties of glass based on compositional and structural information is a fundamental issue with enormous practical and industrial significance for the study of laser glass. Here we address this problem and demonstrate the application of phase diagram method in predicting the spectroscopic properties of Nd³⁺-doped binary and ternary silicate, binary phosphate, and borate laser glasses from their initial congruently melting compounds. In particular, spectroscopic properties, such as effective linewidth (Δλ_eff) and fluorescence branching ratio (β) can be precisely predicted in all glass systems with an error less than 5%. Furthermore, a composition–structure–property database of Nd³⁺-doped ternary silicate glass system is established and preliminarily applied to the composition design and explanation of commercial glass. This study provides interpretable predictions of the optical and spectroscopic properties for Nd³⁺-doped laser glasses.     

Influence of Boron Oxide on the Physicomechanical Properties of Glasses in the Li2O–B2O3–P2O5 System

The mechanical properties of glasses in the Li₂O–B₂O₃–P₂O₅ system are investigated as a function of the boron oxide content in the range from 5 to 30 mol % at a constant lithium oxide content of 45 mol %. It is demonstrated that, as the B₂O₃ content increases, the density of glasses passes through a maximum at 20 mol % B₂O₃ and the molar volume decreases gradually. The elastic modulus and the hardness of glasses monotonically increase with an increase in the B₂O₃ content. An increase in the B₂O₃ content leads to a decrease in the structural strength (measured using the method of three-point bending of fibers) and the fracture toughness (determined by the microindentation technique). The assumption is made that the decrease in the strength characteristics is caused by the phase separation developed in the structure of lithium phosphate glass with an increase in the B₂O₃ content.     

Glass formation in the fluorozirconate systems containing lead fluoride

The glass formation is investigated in the ternary and quaternary systems ZrF₄-PbF₂-LaF₃, ZrF₄-PbF₂-BaF₂, ZrF₄-PbF₂-LaF₃-NaF, and ZrF₄-PbF₂-BaF₂-NaF at a content of zirconium fluoride ZrF₄ in the range 55–70 mol %. In the ternary systems, it has proved to be possible to synthesize only glass-ceramic samples. In the ZrF₄-PbF₂-LaF₃-NaF quaternary system, the glass formation regions are located within the corresponding concentration triangles. In the ZrF₄-PbF₂-BaF₂-NaF quaternary system, the glass formation regions are adjacent to the ZrF₄-BaF₂-NaF ternary system containing 60 mol % ZrF₄. Glasses in the ZrF₄-PbF₂-LaF₃-NaF system are more stable to crystallization than glasses in the ZrF₄-PbF₂-BaF₂-NaF system. The influence of the purity of the initial fluorides on the process of glass formation in the systems under investigation is analyzed.     

Preparation and crystallization of glasses in the system tetrasilicic mica-fluorapatite-diopside

The production of glasses whose composition ranged between tetrasilicic mica and fluorapatite-diopsite 50/50 (in wt.%) was investigated. Glass-ceramics were obtained by both bulk crystallization and sintering of glass powder compacts. The experimental results showed that increasing amount of apatite and diopsite components in the ternary system until 50% mica content generally caused decrease of melting temperature and increasing stability of glass against spontaneous crystallization during cooling after casting. Liquid immiscibility, whose features depend on the particular glass composition, characterized all the investigated glasses but it was more pronounced in the glasses with higher amount of apatite and diopsite components. The investigated glasses are preferably crystallized in bulk form between 700 and 900 °C, resulting in formation of different combinations between mica, fluorapatite and diopsite, depending on the particular composition. The obtained glass-ceramics exhibited attractive aesthetics, structural integrity and dense structure.     

Structure,crystallization, and performances of alkaline-earth boroaluminosilicate sealing glasses for SOFCs

We study the structure, crystallization, and performances of the sealing glasses with the composition (mol.%) of 12Al₂O₃·8B₂O₃·40SiO₂·40RO (R = Mg, Ca, Sr) for solid oxide fuel cells (SOFCs) before and after isothermal treatment at 700°C, which is within the operation temperature range (600-800°C) of SOFCs. The crystallization behavior has been investigated by differential scanning calorimetry and X-ray diffraction under both dynamic and isothermal conditions. The structural evolution is probed using the Raman and nuclear magnetic resonance spectroscopies. The performances of the sealing glasses are characterized in terms of the coefficient of thermal expansion, the crystallization-induced stress at glass–steel interface. We find that strong crystallization occurs at the operation temperature (700°C) far below the crystallization onset temperature measured by DSC. The structure origin of this anomalous crystallization is discussed in terms of structural heterogeneity of the three studied glasses. We determine the residual stress at the interface between the Ca-containing glass and the steel after isothermal treatment at 700°C for 48 h, but this stress does not lead to falling off the glass layer from the steel. This indicates that this glass is a good candidate to be applied in SOFCs.     

Influence of ZrO2 oxide on the properties and crystallization of calcium fluoro-alumino-silicate glasses

The impact of ZrO₂ content of the glass on the formation, properties and crystallization of glass ionomer cements (GICs) was investigated. Glass series based on SiO₂–Al₂O₃–ZrO₂–P₂O₅–CaO–CaF₂ system was synthesized and studied. The cements were characterized using a setting time, flexural strength, fracture toughness and in vitro biocompatibility test. The setting time of the ionomer cement increased with increasing the ZrO₂ content of the glass. The cements showed a slight decrease of cell biocompatibility with increase the ZrO₂ oxide content in the glasses. The results also showed that the flexural strength and the fracture toughness of the cements increased with immersion time and ZrO₂ oxide content. The crystallization characteristics of the glasses were investigated by differential scanning calorimeter (DSC) and X-ray diffraction analysis (XRD). The addition of ZrO₂ oxide in the glasses led to increase both the glass transition and crystallization temperatures. Fluorapatite [Ca₅(PO₄)₃F], mullite [Al₆Si₂O₁₃], cristobalite [SiO₂] and zircon [ZrSiO₄] phases were crystallized from the investigated glasses. The role played by the glass oxide constituents in determining the setting time, mechanical properties and crystallization characteristics of the prepared glass ionomer was discussed.     

Nucleating role of P2O5 in nepheline-based transparent glass-ceramics

The nepheline-based transparent glass-ceramics are promising candidates for cover glass applications in electronic displays owing to their superior mechanical properties (than glasses) and ability to be chemically strengthened. However, our poor understanding about the kinetic and thermodynamic drivers controlling their crystallization processes usually results in their opacification and development of large internal stresses. The present work focuses on the development of nepheline-based nanocrystalline transparent glass-ceramic designed in the Na₂O–Al₂O₃–SiO₂ ternary system nucleated with P₂O₅. The temporal evolution of the phosphate and nepheline nanocrystal formation has been followed using X-ray diffraction, scanning/transmission electron microscopy, and energy-dispersive spectroscopy. The incorporation of P₂O₅ in the glass structure leads to the phase separation resulting in the crystallization of nanocrystalline Na₃PO₄ as an intermediate phase; thus, acting as a nucleating site for volume crystallization of nepheline. The optimization of nucleation and growth profile in the designed composition results in the formation of a transparent glass-ceramic with high optical transmittance (91.5 ± 0.1%).     

Effect of BaO substitution for CaO on the structural and thermal properties of SiO2–B2O3–Al2O3–CaO–Na2O–P2O5 bioactive glass system used for implant coating applications

The present study replaced 3.30 and 9.00 mol.% BaO for CaO in a SiO₂–B₂O₃–Al₂O₃–CaO–Na₂O–P₂O₅ bioactive glass system used for implant coating applications. Variations of the glass structure, thermal properties, cytotoxicity, and radiopacity of glasses were studied. As demonstrated by the results, upon adding barium oxide to the glass structure, the weight density increased significantly, while a slight decrease in oxygen density was determined. Introducing barium oxide into glass composition did not cause any considerable change in the spectra of FTIR and Raman. It was demonstrated that the amount of bridging oxygen in the glass structure remained quite unaffected. The hot stage microscopy evaluations revealed further shrinkage of barium-containing frits due to lower viscosity and hence, higher viscous flow of these glasses. By substituting barium oxide for calcium oxide and increasing its concentration, the glass transition temperature (T_g) and the dilatometric softening temperature (T_d) decreased, while the thermal expansion coefficient increased. Moreover, upon substituting 9 mol.% barium oxide for calcium oxide, a 30 °C reduction in maximum sintering temperature (T_ms) of the glass was obtained, whereas the shrinkage rate was increased 1.7 times. It was indicated that the sintering process of barium-incorporated glasses would easily proceed without any phase crystallization. The barium-incorporated glasses exhibited more radiopacity. Additionally, no cytotoxic effect was caused by the substitution, and the Ba-containing glasses could be used for biomedical applications and implant coating as well.     

Optical and mechanical properties of calcium phosphate glasses

Binary calcium phosphate glasses in the system, xCaO-(100 ? x) P₂O₅ with x = 30, 35, 40, 45, and 50 mol % were prepared by conventional melt quenching technique. The density, molar volume and refractive index of the glasses were found to increase with the increase in CaO content. Structural investigation by FTIR spectroscopy revealed that the substitution of P₂O₅ by CaO depolymerizes the phosphate glass network by systematic conversion of Q³ structural units to Q² structural units by breaking the P-O-P links. From the optical absorption studies, the optical band gap values were found to decrease with increasing CaO content which can be due to increase in the concentration of non-bridging oxygens in the glass network. Vickers hardness increased with the calcium oxide content due to densification. The fracture toughness decreases with the increase in CaO content due to the increase in the bond density between the modifying cations and the non-bridging oxygens in the glass network. It was observed that brittleness increases with the addition of CaO content which can be mainly attributed to the decrease in the molar volume.