Properties, Structure, and Application of Low-Melting Lead–Bismuth Glasses

Glass formation, crystallization, and physicochemical properties, as well as glass structure in the system PbO – ZnO – Bi₂O₃ – B₂O₃ – SiO₂, are investigated in the section with a constant molar content of glass-formers (B₂O₃ + SiO₂) equal to 20%. A nonlinear dependence of glass properties on their composition is established caused by the change of the coordination state of lead ion in glass structure. The developed glasses are recommended for joint and seals in the production of a new generation of physical parameter sensors.     

Influence of the composition of high-lead phosphate glasses on the location of the UV transmission edge and technological quality

This paper reports on the results of an investigation into the influence of the purity of the initial materials used for preparing vitreous lead metaphosphate, the acidity of the phosphate matrix, and the contents of additives of Group I–III and V elements and the second glass-former on the location of the UV transmission edge of simple binary and ternary lead phosphate glasses. It is shown that, even for a binary glass of the composition (mol %) 50PbO · 50P₂O₅, the location of the UV transmission edge can be shifted by ～50 nm on the wavelength scale depending on the purity of the initial reactants. The shift of the UV transmission edge toward the UV spectral range for ternary glasses containing no variable-valence elements other than lead is considerably larger than that for the high-lead phosphate glass of the previously proposed composition involving antimony, niobium, and cerium oxides. It is established that the addition of niobium oxide Nb₂O₅ to lead phosphate glasses brings about a red shift of the UV transmission edge and a change in the crystallization ability of the glasses. Niobium oxide at a content up to 1.5 mol % increases the crystallization ability of the glass, whereas a change in the niobium oxide content from 1.5 to 3.1 mol % results in a decrease in the crystallization ability. It is demonstrated that the crystallization ability of high-lead phosphate glasses increases at a boron oxide content higher than 5 mol %.     

Structural and emission properties of Eu3+‐doped alkaline earth zinc‐phosphate glasses for white LED applications

Quaternary alkaline earth zinc‐phosphate glasses in molar composition (40 ? x)ZnO – 35P₂O₅ – 20RO – 5TiO₂ – xEu₂O₃ (where x=1 and R=Mg, Ca, Sr, and Ba) were prepared by melt quenching technique. These glasses were studied with respect to their thermal, structural, and photoluminescent properties. The maximum value of the glass transition temperature (T_g) was observed for BaO network modifier mixed glass and minimum was observed for MgO network modifier glass. All the glasses were found to be amorphous in nature. The FT‐IR suggested the glasses to be in pyrophosphate structure, which matches with the theoretical estimation of O/P atomic ratio and the maximum depolymerization was observed for glass mixed with BaO network modifier. The intense emission peak was observed at 613 nm (⁵D₀→⁷F₂) under excitation of 392 nm, which matches well with excitation of commercial n‐UV LED chips. The highest emission intensity and quantum efficiency was observed for the glass mixed with BaO network modifier. Based on these results, another set of glass samples was prepared with molar composition (40 ? x)ZnO – 35P₂O₅ – 20BaO – 5TiO₂ – xEu₂O₃ (x=3, 5, 7, and 9) to investigate the optimized emission intensity in these glasses. The glasses exhibited crystalline features along with amorphous nature and a drastic variation in asymmetric ratio at higher concentration (7 and 9 mol%) of Eu₂O₃. The color of emission also shifted from red to reddish orange with increase in the concentration of Eu₂O₃. These glasses are potential candidates to use as a red photoluminsecent component in the field of solid‐state lighting devices.     

Phase Composition and Structure of Aluminum – Coating Composite

Low-melting enamel coatings for household aluminum kitchenware are synthesized. The possibility of formation of low-melting glasses in the system R₂O – Al₂O₃ – B₂O₃ – TiO₂ – P₂O₅ is studied. An optimum glass matrix composition with a decreased firing temperature (580°C) is selected.     

Effective sensitization of Eu3+ ions on Eu3+/Nd3+ co-doped multicomponent borosilicate glasses for visible and NIR luminescence applications

Eu³⁺/Nd³⁺ co-doped multicomponent borosilicate glasses (ND1E: 10BaO +10ZnF₂+10K₂O +20SiO₂+(49-x) B₂O₃+1Nd₂O₃+xEu₂O₃) were prepared by conventional melting and rapid quench technique to evaluate the effect of Eu³⁺ ions in the Nd³⁺ doped glasses. Thermal stability, structural and spectroscopic characteristics of the ND1E glasses were investigated by using DSC, XRD, FTIR, Optical absorption, excitation and emission measurements. The Judd – Ofelt (JO) analysis is implemented to the absorption spectrum of the prepared glassy matrix in order to identify their potential applicability in lasing devices. Enhancement of ⁷F₀ → ⁵L₆ band (394 nm) with the increasing concentration of Eu³⁺ ion in the Nd³⁺ excitation spectra (λ_emi = 1060 nm) reveals the possibility of obtaining the characteristic fluorescence spectra of Nd³⁺ ion with the typical excitation wavelengths (Nd³⁺ = 584 nm and Eu³⁺ = 394 nm) of both rare earth ions and it is further verified from the emission spectrum. This interesting luminescence effect of showing excellent visible and NIR emission under 394 nm excitation mainly attributes the energy transfer mechanism between the RE³⁺ ions and the reason underlying this effect is discussed in detail with the help of partial energy level diagram. Energy transfer efficiency between the Eu³⁺ and Nd³⁺ ions were evaluated by using the radiative lifetimes of the prepared glasses. Also, a comparison of radiative properties and lasing characteristics of Eu³⁺/Nd³⁺ co-doped glasses with other Nd³⁺ glasses are reported. The emission intensities were characterized using CIE chromaticity diagram and the observed CIE coordinates shows a shift towards reddish – orange region with the increase in Eu³⁺ concentration. The quantum efficiency of the prepared glasses was determined experimentally. The obtained results suggest that the ND1E glassy system can be considered as a potential candidate for visible and NIR luminescence applications.     

Oxide ion/electronic polarizability,optical basicity and linear dielectric susceptibility of TeO2 – B2O3 – SiO2 glasses

A system of bio-silica borotellurite glasses was fabricated based on the chemical formula [(TeO₂)_0.7 (B₂O₃)_0.3]_1-x (SiO₂)_x with x = 0.1, 0.2, 0.3, and 0.4 using the melt-quenching technique using silica (98.548% SiO₂, from rice husk), TeO₂ (Alfar Aeser, 99.9%) and B₂O₃ (Alfar Aeser, 99.9%). Measurements and characterizations such as density and molar volume measurements, XRD analysis, FTIR, and UV–Vis spectroscopes were performed on the studied glasses. The objective was to determine the glasses’ applicability in optoelectronics, non-linear optics, and laser technologies through polarizability, linear electric susceptibility, and optical basicity study. Apart from confirming the amorphous nature of the glasses, the XRD analysis identified the presence of a crystalline phase of tellurium oxide (α-TeO₂) formed. The FTIR spectral study revealed the presence of TeO₃, BO₃, and SiO₄ structural units in the studied glasses. The refractive index (2.3026 – 2.2651), molar polarizability (8.0696 – 9.4334 Å³), oxide ion polarizability (3.2970 – 3.6202 Å³), electronic polarizability (0.2296 – 0.2335 Å³), dielectric constant (5.1307 – 5.3019), optical basicity (0.6719 – 0.7998), metallization criterion (0.410853 – 0.420714) and electric susceptibility (0.3286 – 0.3422 esu) of the glasses were presented. With the high refractive index and favourable electronic/oxide ion polarizability as well as good electric susceptibility, the glasses have shown great potential for optical fibre and laser applications. Metallization criterion value falls in the range of glasses with great potentials for non-linear optical application. The dielectric value suggests the glasses represent wideband semiconducting glasses believed to be good for application in microelectronic substrates fabrication.     

Electret Properties of Radiation-Charged Phosphate Glasses

The process of formation of a surface charge in phosphate glasses depending on polarization conditions is investigated. A relationship is established between the chemical composition of glass and its capacity for forming internal electric fields under radiation for glasses of type 0.50P₂O₅ – 0.45RO – 0.05R₂O₃.     

Photoluminescence of terbium doped oxyfluoro-titania-phosphate glasses for green light devices

Terbium (Tb³⁺) doped oxyfluoro-titania-phosphate glasses of chemical composition (in mol%), (60 - x) P₂O₅ – 15 BaF₂ – 20 CaF₂ – 5 TiO₂ – x Tb₄O₇, x?=?0.05, 0.1 and 0.1 were fabricated by usual melt-quenching technique. Photoluminescence (PL) properties of the samples have been investigated by excitation, emission and decay profiles. Upon excitation at 377?nm, the PL spectra exhibit an intense band at 541?nm which corresponds to the ⁵D₄ → ⁷F₅ transition. The intensity ratio of green-to-blue (I_G/I_B) was found to be 9.2 for 0.1?mol% of Tb³⁺-doped glass. High-energy absorption bands were not resolved in the absorption spectrum but disclosed in the photoluminescence excitation spectrum. Decay curves were unveiled non-exponential and mono-exponential behaviours for the ⁵D₃ and ⁵D₄ levels, respectively. Lifetime of the ⁵D₃ and ⁵D₄ levels was decreased up to 0.1?mol%, and thereafter it was increased with the increase of Tb³⁺ ion concentration upon 377?nm excitation. The CIE chromaticity coordinates were supported that the green emission was predominant in Tb³⁺-doped oxyfluoro-titania-phosphate glasses.     

Effects of In2O3 nanoparticles doping on the photoluminescent properties of Eu2+/Eu3+ ions in silica glasses

Eu²⁺/Eu³⁺ ions doped silica glasses contained In₂O₃ nanoparticles (NPs) have been fabricated by using nanoporous silica glasses. Interestingly, efficient energy transfer from In₂O₃ NPs to Eu²⁺/Eu³⁺ ions enhanced the photoluminescence (PL) emission of Eu²⁺/Eu³⁺ ions, which derives from lattice defects in In₂O₃ NPs. Our work has not only demonstrated a facile way to fabricate NPs and rare earth ions co-doped silica glasses, but also extended the applications of semiconductor oxide NPs such as In₂O₃ NPs.     

Enhancement of the radiation resistance of cerium-containing fluorophosphate glasses through codoping with Sb2O3 and Bi2O3

The growing demand for radiation-resistant optical glasses for space and nuclear radiation applications has attracted significant research interest. However, radiation-resistant fluorophosphate glasses have been poorly studied. In this work, we report on the tailoring and performance of radiation-resistant fluorophosphate glasses that contained cerium through codoping with Sb₂O₃ and Bi₂O₃. The physical properties, optical properties, microstructure, and defects of fluorophosphate glasses were investigated using transmittance measurements, absorption measurements, as well as Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and electron paramagnetic resonance (EPR) spectroscopy. The results showed that the radiation resistance of all codoped fluorophosphate glasses was better than the undoped cerium-containing fluorophosphate glasses after 10–250 krad(Si) irradiation. Especially in glasses doped with Bi₂O₃, the optical density increment at 385 nm was only 0.1482 after 250 krad(Si) irradiation. The CeO₂ prevented the development of phosphate-related oxygen hole center (POHC) defects, whereas further codoping with Bi₂O₃ suppressed the formation of oxygen hole center (OHC) and POEC defects, reducing the breaking of phosphate chains caused by CeO₂. Bi³⁺ is more likely than Sb³⁺ to change the valence, affecting the transition equilibrium of intrinsic defects and reducing the concentration of defects produced by irradiation. When codoping with Sb₂O₃ and Bi₂O₃, Bi₂O₃ does not enhance radiation resistance owing to the scission effect of Sb₂O₃ on the phosphate chain, which is not conducive to the radiation resistance of glasses. This indicates that the cerium-containing fluorophosphate glasses doped with Bi₂O₃ can effectively suppress the defects caused by irradiation and improve the radiation resistance of the glasses.     

Phase equilibrium in systems based on oxides of zirconium,lanthanum and samarium

According to the results of the samples studied by X-ray diffraction and microstructural analyzes the phase equilibria in the binary La₂O₃ – Sm₂O₃ and ternary ZrO₂ – La₂O₃ – Sm₂O₃ systems were studied. The boundaries of the phase fields of the binary system are specified and an isothermal cross section of the ternary state diagram of the ZrO₂ – La₂O₃ – Sm₂O₃ system at a temperature of 1500 °C is constructed. No new phases have been identified in the studied systems. It is established that in the ternary system ZrO₂ – La₂O₃ – Sm₂O₃ at 1500 °C fields of solid solutions on the basis of cubic (F) modification with structure of fluorite type, tetragonal (T) modification of ZrO₂, monoclinic (B) modifications of Sm₂O₃, hexagonal (A) are formed. La₂O₃, as well as an ordered phase with a structure of the type of pyrochlore Ln₂Zr₂O₇ (Py). The boundaries of the phase fields and the parameters of the unit cells of the formed phases are determined. A characteristic feature of this isothermal cross section is the formation of a continuous series of solid solutions based on the phase of the pyrochlore type La₂Zr₂O₇ (Sm₂Zr₂O₇). The limiting solubility of Sm₂O₃ in the ordered phase La₂Zr₂O₇ is 16 mol. % along the section Sm₂O₃- (67 mol.% ZrO₂ - 33 mol.% La₂O₃). The solubility of La₂O₃ in the solid solution Sm₂Zr₂O₇ is slightly less and is 11 mol. % along the section La₂O₃- (67 mol.% ZrO₂ - 33 mol.% Sm₂O₃). The isothermal cross-section of the state diagram of the ZrO₂ – La₂O₃ – Sm₂O₃ system at 1500 °C is characterized by the presence of three three-phase (Py + T + F), (A + Py + B), (Py + F + B) and eight two-phase (A + Py), (B + A), (B + Py), (F + B), (T + F), (Py + T), (F + Py-two) areas.     

Opacified Glazes Based on Liquating Glass of Low-Alkali Compositions

The vitrification processes in the Na₂O – MgO – CaO – B₂O₃ – SiO₂ system and the effect of the heat-treatment conditions on the location of the liquation regions, the nature, the structure, and the phase composition of liquating glasses and on the kinetics of the liquation processes are studied. Physicochemical parameters of the glasses that corroborate the presence of liquation-phase inversion are identified. Compositions for liquating glazes with a minimum content of zirconium-bearing opacifying components are developed.     

Tinted Low-Melting Enamels for Aluminum

The possibility of formation of low-melting glasses in the R₂O – RO – Al₂O₃ – B₂O₃ – TiO₂ – P₂O₅ system at a firing temperature of 550°C is investigated. A correlation of glass formation in the considered system with the content of Al₂O₃ and P₂O₅ is established, and the composition of a transition layer with crystalline phases of Na₂O · P₂O₅, Al₂O₃ and Al₂O₃ · P₂O₅ is determined.     

Elucidating the Effect of Iron Speciation (Fe2+/Fe3+) on Crystallization Kinetics of Sodium Aluminosilicate Glasses

We report on the influence of Fe₂O₃ on the crystallization kinetics of nepheline (Na₂O·Al₂O₃·2SiO₂)‐based sodium aluminosilicate glasses. A series of glasses with varying Al₂O₃/Fe₂O₃ content were synthesized in the system 25Na₂O–(25–x) Al₂O₃–xFe₂O₃–50SiO₂ (x varies between 0 and 5 mol%) through melt‐quench technique. A systematic set of experiments were performed to elucidate the influence of iron speciation (Fe²⁺/Fe³⁺) on the crystallization kinetics of these glasses including: (1) obtaining the details of nonisothermal crystallization kinetics by differential scanning calorimetry, (2) determining the influence of heat treatment on the structure and iron coordination in glasses by X‐ray photoelectron spectroscopy and wet chemistry, and (3) following the crystalline phase evolution in glasses in air and inert environments by X‐ray diffraction and scanning electron microscopy. The crystallization of two polymorphs of NaAlSiO₄—carnegieite (orthorhombic) and nepheline (hexagonal)—was observed in all the glasses, wherein the incorporation of iron promotes the formation of nepheline over carnegieite while shifting the crystallization mechanism from surface to volume. The influence of environment (air versus inert) and iron content on the crystallization kinetics of these glasses is contextualized from the perspective of the devitrification problem usually observed in sodium‐ and alumina‐rich high level nuclear waste glasses.     

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.     

Self-reduction of Eu3+ to Eu2+ in europium-doped Li2B4O7 glass prepared in air

Motivated by the detection of neutrons, europium-doped Li₂B₄O₇ glasses enriched with both lithium and boron elements with high cross-section capture were developed. A highly effective method of realizing the self-reduction of Eu³⁺ to Eu²⁺ ions in europium-doped Li₂B₄O₇ glasses prepared by high temperature melt-quenching technology in air was revealed. The self-reduction of Eu³⁺ to Eu²⁺ ions can be easily achieved by the partial replacement of B₂O₃ with BN within 2 mol% concentration. And the effect of partially replacing B₂O₃ with BN on the optical properties of europium-doped Li₂B₄O₇ glass are systematically studied by transmittance, photoluminescence, and radioluminescence spectra, together with the luminescence decay curves.     

Low-Melting Glasses Based on Borate Systems

The results of analyzing systems of low-melting glasses and their application areas based on published data are used to select an optimum system. The melting properties of low-melting glasses based on the borate system ZnO – SrO – B₂O₃ are studied. The dependences of the main properties of glasses (TCLE, softening temperature, microhardness, chemical resistance to water) on their compositions are determined. The optimum low-melting glass compositions with required physicochemical and technological parameters are identified.     

Fabrication,tunable fluorescence emission and energy transfer of Tm3+-Dy3+ co-activated P2O5–B2O3–SrO–K2O glasses

A growing demand for white light-emitting diodes (W-LEDs) gives rise to continuous exploration of functional fluorescence glasses. In this paper, Tm³⁺/Dy³⁺ single- and co-doped glasses with composition (in mol%) of 30P₂O₅–10B₂O₃–23SrO–37K₂O were synthesized using the melt-quenching method in air. The physical properties, glass structure, luminescence characteristics and energy transfer mechanism of the glasses were systematically studied. As glass network modifiers, Tm³⁺ and Dy³⁺ ions can densify the glass structure. Excitation wavelength and doping concentration of Tm³⁺/Dy³⁺ ions have a direct impact on the emission intensities of blue and orange light as well as the color coordinate of the as-prepared glasses. A white light very close to standard white light can be obtained under 354 nm excitation when the content of Tm³⁺ and Dy³⁺ is 0.2 mol% and 1.0 mol%, respectively. The results of the emission spectra and decay curves reveal the existence of energy transfer from Tm³⁺ to Dy³⁺. The analytic results based on the Inokuti-Hirayama model indicate that the electrical dipole-dipole interaction may be the main mechanism of energy transfer. Moreover, Tm³⁺/Dy³⁺ co-activated glass phosphor has good thermal stability and chrominance stability and it is a promising candidate for white LEDs and display device.     

Synthesis and Spectral Properties of Nd<Subscript>2</Subscript>O<Subscript>3</Subscript>-Doped Sodium Silicophosphate Glass

Combined UV-visible and FTIR spectral studies of undoped and Nd₂O₃ –doped sodium silicophosphate glasses were carried out to characterize the optical and structural properties of such glasses. The base undoped silicophosphate glass exhibits strong UV absorption which is due to the presence of unavoidable trace iron impurities (mainly Fe³⁺ ions) present contaminated within the raw materials used for the preparation of such glasses. Nd₂O₃ –doped glasses show characteristic absorption bands extending in the entire visible region which are attributed to the contribution of Nd³⁺ ions with distinct peaks which are almost constant with the increase of dopant. This comes from the combined compact glass structure containing two glass forming units and the shielding of the rare-earth ions. Infrared absorption spectra of the studied glasses reveal characteristic IR bands due to the combination of both silicate and phosphate groups. The introduction of Nd₂O₃ within the dopant level (2 %) produces no variations in the IR vibrational bands due to the presence of the two structural silicate and phosphate groups giving compactness of the network structure. The deconvoluted spectra reveal the presence of phosphate groups in a slightly high ratio due to the high content of P₂O₅ in the composition.     

Thermal and structural modification in transparent and magnetic germanoborate glasses induced by Gd2O3

A series of new transparent and magnetic germanoborate glasses in the system (100-x)[60GeO₂–25B₂O₃–10Na₂O–4Al₂O₃–1PbO] – (x) Gd₂O₃, with x = 0, 1, 2, 5, 10, 15 and 20 mol%, was prepared and studied with respect to their thermal and structural changes in the presence of Gd₂O₃. Based on Differential Scanning Calorimetre (DSC) analysis, a glass with 5% of Gd₂O₃ showed a high thermal stability, which progressively decreases for samples with higher content of Gd₂O₃. By the analysis of Raman and Fourier Transform Infrared (FTIR) spectra, it was possible to identify that by increasing the amount of Gd₂O₃, a progressive depolymerization of 6-membered Ge^[IV] rings is promoted, concomitant with an increase of Ge^[IV] tetrahedra units with non-briding oxygens. The structural analysis through the local-sensitive techniques EXAFS (Extended X-ray Absorption Fine Structure) and XANES (X-ray Absorption Near Edge Structure) showed that the short-range structural modification around the elements Ge and Gd³⁺ does not change with the addition of Gd₂O₃ and the presence of germanium four-fold coordination [Ge^IV] and Gd³⁺ states, respectively. A simulation of the coordination number (N), the interatomic distance (R) of Ge–O and Gd–O bonds and the Debye-Waller factor was also carried out. The microstructure_, after crystallization, of the sample with 15 mol% of Gd₂O₃ was evaluated using optical and electron microscopes. Finally, the paramagnetic behaviour and ion probe quantification of Gd³⁺ ions were obtained based on magnetic susceptibility measurements.