Effect of glass composition on the hardness of surface layers on aluminosilicate glasses formed through reaction with strong acid

The effect of glass composition on physico‐chemical properties of surface layers formed through reaction between strong acid and several silicate and aluminosilicate glasses was studied through transmission‐IR, ATR‐IR, XPS, SIMS, and nano‐indentation analyses. It was shown that aluminum is depleted from the surface while molecular water is diffused into the surface layer of glasses with high levels of aluminum. Nano‐indentation experiments indicated that the hardness of the surface layers were decreased compared to that of the bulk region and the degree of the softening was more significant in the high aluminum glass.     

Interpreting the optical properties of oxide glasses with machine learning and Shapely additive explanations

Due to their excellent optical properties, glasses are used for various applications ranging from smartphone screens to telescopes. Developing compositions with tailored Abbe number (V_d) and refractive index at 587.6 nm (n_d), two crucial optical properties, is a major challenge. To this extent, machine learning (ML) approaches have been successfully used to develop composition–property models. However, these models are essentially black boxes in nature and suffer from the lack of interpretability. In this paper, we demonstrate the use of ML models to predict the composition-dependent variations of V_d and n_d. Further, using Shapely additive explanations (SHAP), we interpret the ML models to identify the contribution of each of the input components toward target prediction. We observe that glass formers such as SiO₂, B₂O₃, and P₂O₅ and intermediates such as TiO₂, PbO, and Bi₂O₃ play a significant role in controlling the optical properties. Interestingly, components contributing toward increasing the n_d are found to decrease the V_d and vice versa. Finally, we develop the Abbe diagram, using the ML models, allowing accelerated discovery of new glasses for optical properties beyond the experimental pareto front. Overall, employing explainable ML, we predict and interpret the compositional control on the optical properties of oxide glasses.     

Thermal and optical properties of La2O3–Ga2O3– (Nb2O5 or Ta2O5) ternary glasses

La₂O₃–Ga₂O₃–M₂O₅ (M = Nb or Ta) ternary glasses were fabricated using an aerodynamic levitation technique, and their glass‐forming regions and thermal and optical properties were investigated. Incorporation of adequate amounts of Nb₂O₅ and Ta₂O₅ drastically improved the thermal stabilities of the glasses against crystallization. Optical transmittance measurements revealed that all the glasses were transparent over a wide wavelength range from the ultraviolet to the mid‐infrared. The refractive indices of the glasses increased and the Abbe number decreased upon substituting Ga₂O₃ with Nb₂O₅, and the decrease in the Abbe number was significantly suppressed when Ta₂O₅ was incorporated into the glass. As a result, excellent compatibility between high refractive index and lower wavelength dispersion was realized in La₂O₃–Ga₂O₃–Ta₂O₅ glasses. Analysis based on the single‐oscillator Drude–Voigt model provided more systematical information and revealed that this compatibility was due to an increase in the electron density of the glass.     

Crystallization,mechanical, and optical properties of transparent,nanocrystalline gahnite glass‐ceramics

This paper describes the preparation of a transparent glass‐ceramic from the SiO₂‐K₂O‐ZnO‐Al₂O₃‐TiO₂ system containing a single crystalline phase, gahnite (ZnAl₂O₄). TiO₂ was used as a nucleating agent for the heat‐induced precipitation of gahnite crystals of 5‐10 nm. The evolution of the ZnAl₂O₄ spinel structure through the gradual formation of Al‐O bonds was examined by infrared spectroscopy. The dark brown color of the transparent precursor glass and glass‐ceramic was eliminated using CeO₂. The increase in transparency of the CeO₂‐doped glass and glass‐ceramics was demonstrated by UV‐visible absorption spectroscopy. EPR measurements confirmed the presence of Ce³⁺ ions, indicating that CeO₂ was effective in eliminating the brown color introduced by Ti³⁺ ions via oxidation to Ti⁺⁴. The hardness of the glass‐ceramic was 30% higher than that of the as‐prepared glasses. This work offers key guidelines to produce hard, transparent glass‐ceramics which may be potential candidates for a variety of technological applications, such as armor and display panels.     

Self‐limited crystallization‐mediated removal of hydroxyl in glass

The effective removal of hydroxyl groups (OH) is receiving the attention of scientists interested in developing high‐performance photonic glass. Previous approaches rely on stringent control of the various drying techniques which meet with limited success in silicate glass obtained by the sol‐gel method. Here, we present a novel in situ strategy to remove structural OH groups, based on the self‐limited nanocrystallization‐triggered local chemical reaction between OH and F^? in the glassy phase. The experimental data revealed that a more than 100‐fold increase in the emission intensity can be realized. Moreover, the mechanism was discussed and it can be attributed to the effective removal of structural OH with especially strong binding energy. The results suggest an innovative avenue for the development of photonic glasses with efficient luminescence, excellent optical transmission, and improved reliability.     

Compositional dependence of crystallization in Ge–Sb–Se glasses relevant to optical fiber making

For fiber‐optic mid‐infrared bio‐ and chemical‐sensing, Ge–Sb–Se glass optical fibers are more attractive than Ge–As–Se because of: (i) lowered toxicity and (ii) lower phonon energy and hence transmission to longer wavelengths, with potential to reach the spectral “fingerprint region” for molecular sensing. There is little previous work on Ge–Sb–Se fibers. Here, fibers are fabricated from two glass compositions in the Ge_xSb₁₀Se_90?x atomic (at.) % series. Both glass compositions are of similar mean‐coordination‐number, lying in the overconstrained region, yet of different chemical composition: stoichiometric Ge₂₅Sb₁₀Se₆₅ at. % and non‐stoichiometric Ge₂₀Sb₁₀Se₇₀ at. %. Thermal analysis on bulk glasses has previously shown that the former exhibited the maximum glass stability of the series. However, during fiber‐drawing of Ge₂₅Sb₁₀Se₆₅ at. %, the preform tip is found to undergo surface‐devitrification to monoclinic GeSe₂ alone, the primary phase, no matter if the preform is an annealed, as‐melted rod or annealed, extruded rod. The heating rate of the preform‐tip to the fiber‐drawing temperature is estimated to be up to ~100°C/min to ~490°C. Lower heating rates of 10°C/min using thermal analysis, in contrast, encourage crystallization of both Sb₂Se₃ and GeSe₂. The non‐stoichiometric: Ge₂₀Sb₁₀Se₇₀ at. % composition drew successfully to low optical loss fiber, no matter whether the preform was an annealed, as‐melted rod or annealed, extruded rod.     

Er3+-doped antimony-silica glass and fiber for broadband optical amplification

In this paper, the synthesis, structure, and optical analysis of Er³⁺-doped antimony-silica glass system are reported. The hybridization of Si with Sb ions is found to be favorable for reducing the phonon energy of the glass system. The optical properties, including the emission intensity and bandwidth, can be simultaneously improved. Notably, the full width at half maxima (FWHM) of near-infrared emission from Er³⁺ can be broadened from 61 to 82 nm. Furthermore, the antimony-silica glass fiber is successfully prepared, and the luminescence and gain performance of the fiber are characterized. The antimony-silica glass exhibits excellent fiber-forming ability, and the obtained fiber shows excellent gain performance. The results suggest that antimony-silica glass is a promising gain material for fiber amplifier and laser.     

Atomic and micro-structure features of nanoporous aluminosilicate glasses from reactive molecular dynamics simulations

Long-term chemical durability of borosilicate glasses that makes them a widely accepted form of nuclear waste disposal is achieved through the formation of a porous aluminosilicate gel layer that provides passivity and limits the transport of water to the reaction front. Detailed understanding of the porous silicate gel layer is thus critical in elucidating the corrosion mechanism of these glasses and to design of new glass composition for waste immobilization and other applications. In this paper, we use the diffuse charge reactive potential to generate porous aluminosilicate glass structures with compositions equivalent to the gel layers formed at the glass-water interface with an aim to understand the processing condition on the microstructure and atomic structure of these systems. We demonstrate the use of the charge scaling techniques is an effective approach to generate these porous structures with controllable pore mophologies. After initial validation of the potentials and calcium aluminosilicate glass structures using neutron diffraction, we created gel structures with compositions similar to well-known model nuclear waste borosilicate glasses. The porosities and the pore size distribution bear a strong correlation to the processing temperature, as well as to the local atomic structure. Thus, by controlling the processing parameters, the generated porous structures can be customized to closely resemble gel structures due to borosilicate glass corrosion. These results provide insights of the micro- and atomic structure features of the porous aluminosilicate glasses and on the optimal procedure to generate porous structures that can be comparable to experimentally observed gel layer structures thus to elaborate on the correlations between the structure and phenomena in glass-water interactions.     

Review of tellurite glasses purification issues for mid-IR optical fiber applications

We reviewed the tellurite glass purification studies performed over the last 20 years, in particular dealing with the mid-infrared (mid-IR) transmission performances. Best results are obtained under rich O₂ atmosphere with platinum crucibles although Gibbs energy calculations show that other crucibles material are possible such as gold or alumina. From the point of view of the thermodynamics of involved oxidation reactions only, we identified the suitable conditions based on Gibbs energy calculations to be a synthesis temperature set above 900 K and a O₂ pressure around 10⁵ Pa. The performances of the different purification techniques were also compared. Finally, we analyzed the tellurite fibers recently optimized for mid-IR which present low attenuation up to 4 µm allowing supercontinuum generation up to 5 µm.     

Nonlinear negative transmittance at a CW 980‐nm laser diodes pumping in Yb3+:CaF2 nanocrystals‐embedded glass ceramics

Cooperative upconversion luminescence (CUCL) occurs in spectral regions in which single ions do not have energy levels. However, all results reported so far are concentrated on luminescence properties from Yb³⁺ ions‐doped various hosts. Here, we report the observation of nonlinear negative transmittance (NNT) at continuous‐wavelength (CW) 980‐nm laser diodes (LDs) pumping in silicate oxyfluoride glass ceramics (GCs)‐containing CaF₂:Yb³⁺ nanocrystals. The unique optical nonlinearity is analyzed based on energy‐level transitions, dynamic evolution, rate equation, and power transmission equation, which can be explained as the cooperative optical absorption for the intense CUCL of Yb³⁺ ions. The NNT in the CaF₂:Yb³⁺ nanocrystals‐embedded GCs can be tailored with the power of a CW 980‐nm LDs, which possesses potential for the development of future optical limiters and switches.     

Intrinsic second-order nonlinearity in chalcogenide glasses containing HgI2

Frequency conversion using nonlinear optical (NLO) crystals is widely used in advanced photonic technologies to produce coherent light in the spectral regions where the available laser sources are missing. Isotropic glasses usually do not show second order nonlinear processes like second harmonic or difference frequency generation (SHG, DFG) except for temporarily induced anisotropy under external stimuli. Here, we show that a HgI₂–Ga₂S₃–GeS₂ homogeneous glass exhibits a strong intrinsic SHG response comparable with that of the well-known NLO single crystal LiNbO₃. The origin of this extremely rare phenomenon seems to be noncentrosymmetric bent HgI₂ molecules embedded in a sulfide glassy host. Taking into account the unique properties of chalcogenide glasses (wide IR transmission, low phonon density, unlimited ability to be modified changing the appropriate glass properties, fiber drawing and thin layer design), the observed phenomenon opens up the possibility of creating fundamentally new devices for mid-IR photonics.     

Role of Nd3+ ions on the nucleation and growth of PbS quantum dots (QDs) in silicate glasses

The influence of Nd₂O₃ addition on the precipitation kinetics of lead chalcogenide (PbS) quantum dots (QDs) in silicate glasses was investigated. Energy dispersive X‐ray spectroscopy (EDS) indicated that the Nd³⁺ ions are preferentially located inside the PbS QDs rather than in the glass matrix. Changes in diameter (D) of PbS QDs exhibited smaller time dependencies (i.e., D≈t^{0.270‐0.286}) than that predicted by the classical Lifshitz–Slyozov–Wagner (LSW) theory. This is due to the limited concentrations of Pb²⁺ and S^2? ions and the large diffusion distance inside the glass matrix. In addition, extended X‐ray absorption fine structure (EXAFS) results indicated that the formation of PbS QDs was retarded due to the presence of Nd₂O₃ in the glasses, as the large NdO_x polyhedra interrupt the diffusion of Pb²⁺ and S^2? ions. We believe that these Nd³⁺ ions are primarily located in PbS QDs in the form of Nd–O clusters, and that the PbS QDs are built on top of these clusters.     

Optical Amplification at 1.3 μm in a Praseodymium-Doped Sulfide-Glass Fiber

Praseodymium-doped glasses were prepared in the Ga-Na-S (GNS) system and their optical properties were studied. A single-mode fiber with an attenuation loss of 1.2 dB/m at a wavelength of 1.31 μm was fabricated using an extrusion method, and the amplification characteristics were measured in the bidirectional pumping configuration. We demonstrated a gain coefficient of 0.81 dB/mW at a wavelength of 1.34 μm, which is the highest we have ever reported, and achieved a net gain of 32 dB for a pump power of 90 mW. Highly efficient optical amplification at a wavelength of 1.3 μm was demonstrated in the praseodymium-doped GNS fiber.     

Novel gallate-based oxide and oxyfluoride glasses with wide transparency,high refractive indices,and low dispersions

The glass-forming region of a BaO-La₂O₃-Ga₂O₃ ternary system was confirmed and BaF₂-BaO-La₂O₃-Ga₂O₃ new oxyfluoride glasses were prepared by a containerless processing. We also analyzed the physical, thermal, and optical properties of new oxide and oxyfluoride glasses. The direct effects of the substitution of oxygen by fluorine and the effect of BaO and La₂O₃ on the refractive index and Abbe number were discussed on the basis of electronic polarizability and resonance wavelength of oscillator. The refractive indices increased with increasing La₂O₃ concentration because La₂O₃ increased the electronic polarizabilities. Abbe number increased with increasing BaO and fluorine concentration because of the decrease in resonance wavelength of oscillator. By the combination of the BaO, La₂O₃, and fluorine in the gallate glass system, we could obtain novel oxide and oxyfluoride glasses with high refractive index (1.81-1.95) and high Abbe number (31-55). The absorption edge in UV region shifted to the shorter wavelength and IR cut-off wavelength shifted to the longer wavelength with increasing fluorine. Therefore, wide transparent glass was obtained from 262 nm to 11.3 μm.     

The nonlinear optical properties of silver nanoparticles decorated glass obtained from sintering mesoporous powders

Silver nanoparticles (Ag NPs) have excellent third-order nonlinear optical properties but it is still difficult to obtain silica glass containing Ag NPs with homogenous dispersion and small particle size. Herein, silica glass with homogenously distributed Ag NPs in its matrix was derived from sintering a famous type of mesoporous silica (FDU-12) encapsulated with Ag NPs (Ag NPs/FDU-12) through Spark Plasma Sintering (SPS) technique. Benefited from the low-temperature sintering property of the Ag NPs/FDU-12 powders (~930°C within 5 min), the Ag NPs can be directly trapped in the derived silica glass with small particle size (<3.0 nm) and without mass loss. The as-prepared Ag NPs/glass showed a typical reverse saturable absorption curve, which is measured via the Z-scan method by using a 532 nm nanosecond laser. The nonlinear coefficient and imaginary third-order susceptibility were calculated as 11.46 cm/GW and 2.22 × 10⁻¹² esu, respectively, indicating the excellent third-order nonlinear optical properties of the Ag NPs/glass. This study demonstrates a great potential for preparing silica glasses functionalized with well dispersed ultrafine functional particles, which is appealing in photonic field.     

Ultrafast Optical Switches and Wavelength Division Multiplexing (WDM) Amplifiers Based on Bismuth Oxide Glasses

Glasses with a high refractive index exhibit interesting properties. All optical switching and broadband amplification performances have been demonstrated using glasses based on bismuth oxide (Bi₂O₃). Optical Kerr shutter (OKS) switching and degenerated four-wave mixing experiments for nonresonant-type Bi₂O₃–B₂O₃–SiO₂ glasses have been performed using femtosecond lasers. This glass exhibits an ultrafast response (<150 fs) in OKS operation. Moreover, terahertz-range (THz-range) optical switching has been successfully performed with this glass, using a 1.5-THz pulse train. Erbium-doped bismuth-based oxide glasses also have been prepared for wavelength division multiplexing (WDM) amplifiers. These glasses exhibit broadband emission and negligible concentration quenching, which indicates that the bismuth-based glass is suitable for broadband amplifiers and highly doped short-length fiber applications for metro use.     

Optical properties of bismuth tellurite based glass

A series of binary tellurite based glasses (Bi(2)O(3))(x) (TeO(2))(100-) (x) was prepared by melt quenching method. The density, molar volume and refractive index increase when bismuth ions Bi(3+) increase, this is due to the increased polarization of the ions Bi(3+) and the enhanced formation of non-bridging oxygen (NBO). The Fourier transform infrared spectroscopy (FTIR) results show the bonding of the glass sample and the optical band gap, E(opt) decreases while the refractive index increases when the ion Bi(3+) content increases.     

Improvement in electrical properties of thermoelectric CuAlO2 ceramics aided by aluminosilicate glass

Delafossite CuAlO₂ (CAO) ceramics were fabricated by the solid‐state route, using aluminosilicate glass powders as a sintering aid to improve the sintering ability and electrical conductivity, at 1473 K for 3 hours. The CAO ceramics with glass addition obviously enhanced bulk density, grain size, and electrical conductivity. It is found that the conductivity of CAO ceramics increased with the increase in glass content under 9.5%, whereas it was over 9.5%, the conductivity went down. The glass coming up to 9.5% increased the sintering ability and the electrical conductivity which was increased by one order of magnitude, thus increasing the figure of merit ZT for thermoelectric performance of our CAO added with 9.5% glass up to 9.82 × 10^?3 at 773 K, which is a high value among the CAO ceramics. Besides, the impedance analysis shows that the impedance of the CAO ceramic was controlled by its grain boundary.     

Surface Analysis and Treatment of Extruded Fluoride Phosphate Glass Preforms for Optical Fiber Fabrication

Fabrication of fluoride phosphate glass optical fibers using the extrusion method for preform fabrication has been studied using the commercial Schott N‐FK51A glass. The extrusion step was found to create a surface layer of differing composition from the bulk glass material, leading to defects drawn down onto the optical fiber surface during fiber fabrication, resulting in high loss and fragile fibers. Similar phenomena have also been observed in other fluoride‐based glasses. Removal of this surface layer from preforms prior to fiber drawing was shown to improve optical fiber loss from >5 dB/m to 0.5–1.0 dB/m. The removal of this surface layer is therefore necessary to produce low‐loss fluoride phosphate optical fibers.     

Structure and physical properties of Ge15Sb20Se65‐xSx glasses

We explored the structure and physical properties of Ge₁₅Sb₂₀Se_65‐xS_x (with x = 0, 16.25, 32.5, 48.75, and 65) glasses in order to screen the best compositions for the applications in photonics, since the laser damage thresholds in Se‐based glasses are too low although their optical nonlinearities are high. We found that, linear and nonlinear refractive index of the glasses decreased, but glass transition temperature T_g, optical bandgap E_g and the laser damage threshold increased with increasing S content. We further employed Raman scattering and high‐resolution X‐ray photoelectron spectra to probe the structure of the glasses. Through the analysis of the evolution of the different structural units in the glasses, it was concluded that, the heteropolar bonds (Ge–Se/S, Sb–Se/S) were dominated in these glasses. With the increase in chalcogen Se/S ratio, the number of the Se‐related chemical bonds (Ge–Se, Sb–Se and Se–Se) increased and that of S‐related chemical bond (Ge–S, Sb–S and S–S) decreased gradually, and Ge was prior to bond with S rather than Se. The elemental substitution thus had negligible effect on the glass structure. The change of the physical properties was mainly due to the difference of the strength of the chemical bonds between S–Ge(Sb) and Se–Ge(Sb).