Multicomponent Silicate Research Articles

Structural study of the origin of the largest 1.5 μm Er3 + luminescence band width in multicomponent silicate glass

We report the 1.5μm emission band broadening of Er3+ observed in multicomponent SiO2–GeO2–B2O3–Na2O glasses. The largest bandwidth Δλeff=95.6nm was obtained in glass with a composition of 66.75% SiO2–13% GeO2–6% B2O3–4.45% Na2O in wt.%. The band broadening was found to be dealt with: 1) high Er3+ concentration broadening; 2) Yb3+ co-doped broadening; 3) B2O3 broadening; and 4) the reduction of Na2O content broadening. FT-IR spectra showed that the network structure of glasses changed with the glass compositions, which was proven by the significant change of the vibration band of SiO at 1100cm−1 in the shape and intensity. It resulted in a significant change of the local environment of Er3+ ions and evidenced the variation of bond covalence between Er ions and local ligands. The high Judd–Ofelt parameters influenced the broad band emission for these low refractive index (1.50–1.54) glasses.

GeO2 influence on the formation of near-infrared emitting centers in Bi-doped multicomponent silicate glasses

A meaningful increase in the number of NIR emission centers was experimentally observed in bismuth-doped multicomponent silicate glasses additionally doped with germanium dioxide. The emission and excitation spectra of the glass sets were monitored and compared with the spectra of radiative oxygen-deficient centers in vitreous silica and germania.

Environmental effects on initiation and propagation of surface defects on silicate glasses: scratch and fracture toughness study

The glass composition and surrounding environment can play an important role in the initiation and propagation of surface defects, which affect the practical strength of glass. We have studied how the environment and glass composition affect the tribological and indentation properties of multicomponent silicate glasses. Soda lime silica and aluminosilicate glasses were studied to compare the effects of the alkali ion and glass network type on surface defect formation. Although both glasses contained leachable sodium ions, the surface wear of soda lime glass decreased with increasing humidity while sodium aluminosilicate glass had an observable increase in surface wear. This indicated that sodium ion and water activity on/in glass surfaces vary depending on the glass network structure. The exchange of Na+ with K+ in aluminosilicate glass increased the elastic modulus, hardness, and resistance to fracture substantially; however, it did not improve the surface scratch resistance in humid environments. This suggested that the improved fracture toughness for the K-exchanged aluminosilicate glass is mainly due to the improved bulk properties; surface wear can readily take place regardless of Na/K-exchange.

Spectroscopic study of high Er and Er/Yb concentration doped photosensitive silicate glasses for integrated optics application

Er and Er/Yb doped photosensitive multicomponent silicate glasses with composition of 60SiO2–10GeO2–10B2O3–20Na2O (in wt.%) were prepared and characterized in terms of absorption cross-section (σa), fluorescence lifetime (τm) and concentration quenching effect. The solubility of rare earth ions in this glass is much higher (to 2wt.%) than that of conventional silicate glasses, with corresponding lifetime and quantum efficiency of τm=7.5ms and η=50%, respectively. Glasses with different Er/Yb ratios were also made to investigate the effects of Er/Yb ratios on energy transfer efficiency. A ratio of Er/Yb=0.4 showed higher absorption cross-section compared to 0.2 and 0.6. The lifetime for all samples decreased with the addition of Yb2O3. We also report on the 1.5μm emission line broadening of Er3+ ion emission in these glasses. The emission of full width at half maximum shifted from 25.7nm to 48.2nm and the increased line width was found to correlate to an increase in Er3+ concentration in such a multicomponent glass. The studied glass with multifunctional properties is proved to be a very good candidate for application in integrated optics.

Subsolidus isothermal fractional crystallization

In theory, multicomponent silicate liquids of minimum or eutectic composition should crystallize their solidus phases simultaneously and in their invariant proportions. In reality, the crystallization of those liquids of granitic composition produces sequential assemblages and normal fractional crystallization of solid solutions when crystallization commences at or along an isotherm well below the solidus of the system. The sequence of mineral assemblages derives principally from their relative stabilities, as measured by the Gibbs free energy change for the reaction of melt to crystals in the metastable region below the liquidus surface, rather than chemical concentration alone. Whereas crystallization close to the solidus (Δ T ≈ 50 °C) promotes the simultaneous (eutectic) crystallization of quartz and feldspars that leads to the formation of granite, large liquidus undercooling (Δ T ≈ 200 °C) produces sequential assemblages from the margins to centers of melt bodies. The liquidus undercooling that drives subsolidus isothermal fractional crystallization is the single-most important process for the generation of zoned granitic pegmatites.

Ionic and Electronic Mobility in Multicomponent Olivine Silicate Cathode Materials for Li-ion Batteries

In this work, we performed ab initio calculations within the density-functional theory framework to study the electrochemical and kinetic properties of silicate materials with the olivine morphology, that can be suitable for the cathode of rechargeable Li-ion batteries. Our study shows that the migration barriers for polaron-Li complex diffusion in the multicomponent silicates are in a reasonable range (227–248 meV), compared to similar systems. The results show that, although the Li vacancies are strongly bounded to polarons, these materials might not be as insulating as previously assumed, provided that an adequate carrier concentration can be achieved. The effects of the different transition metals on the local structure, electrochemical and electronic properties and on the kinetic mobility of the polaron-Li ion complex are discussed, showing a useful strategy to tailor the electrochemical properties of this family of silicate cathode materials, in order to enhance the energy density and rate capability of the Li-ion battery.

Coloration of Ce-doped Multicomponent Silicate Glasses by Electron Irradiation

The coloration of Ce-doped multicomponent silicate glass (type K509) irradiated by 10 MeV electrons was investigated by absorption spectra, electron paramagnetic resonance and photoluminescence spectra. The results show that non-bridging oxygen hole centers (HC1 and HC2) are induced in K509 glasses after electron irradiation, leading to significant degradation of visible transmission. The concentration of color center grows in an exponential law with the increase of radiation dose at the same dose rate, and decreases in exponential decay law with radiation dose rate at the same total dose. According to photoluminescence spectra, the concentration of Ce ions has a negative correlation with radiation dose, and has a positive correlation with dose rate, which proves the mechanism of radiation-hardness in cerium-doped glasses. Ce ions capturing holes induced by electron irradiation to form Ce inhibits the formation of hole trapped color centers, HC1 and HC2, which avoids additional absorption in visible light range. The energy level diagram of Ce in K509 glasses is also obtained by Gaussian resolution of the broad asymmetric emission spectra of Ce.

大模场掺镱双包层光子晶体光纤内包层新型结构研究

Yb3 +doped multicomponent silicate used as photonic crystal fiber core material was prepared. Its refractive index is 1. 586,efficient half width of the fluorescent spectrum band is 85. 3 nm,and fluorescence lifetime is 1. 30 ms. The influences of structural parameter on the normalized frequency( single mode cutoff condition),numerical aperture,effective mode area,nonlinear effect,and limit loss of the photonic crystal fiber were investigated. Using Yb3 +doped silicate as fiber core material,an octagonal and five layer air hole structure based photonic crystal fiber was designed. The performances of the photonic crystal fiber were digitally simulated using the limited element method. The calculated results indicate that the effective mode field area is 1 150 μm2and the numerical aperture of the inner clad is 0. 45 when the aperture of the air hole is 21. 6 μm and the space between the air holes is 60 μm.

Absorption and scattering in photo-thermo-refractive glass induced by UV-exposure and thermal development

Photo-thermo-refractive (PTR) glass is a multicomponent photosensitive silicate glass that, after successive UV-exposure and thermal treatment, exhibits a refractive index change that results from the precipitation of nano-crystalline NaF. This glass is successfully used for the fabrication of holographic optical elements (volume Bragg gratings) that dramatically enhance properties of numerous laser systems and spectrometers. In this paper, induced absorption and scattering that determine efficiency of such elements were studied. It is found that the main contribution to induced absorption is produced by several types of silver containing particles having absorption bands with maxima in the blue-green region with exponential tails extending to the near IR spectral region. Evolution of all absorption bands was studied for different conditions of UV exposure and thermal development. Complex mechanisms of interconversion of silver containing particles is demonstrated as well as the fact that some of these particles can be associated with catalyzers of the nucleation process. It is also found that induced scattering obeys the classic Rayleigh law with an intensity depending on the conditions of UV exposure and thermal development. For short development times, scattering increases with dosage because of increased volume fraction of crystalline phase. For long development times, scattering decreases with dosage because of decreased size of individual crystals.

Effect of Tm2O3 concentration and hydroxyl content on the emission properties of Tm doped silicate glasses

Tm2O3-doped multi-component silicate glasses without alkali ions are prepared using a conventional melt quenching method. The Judd–Ofelt theory is applied to calculate the intensity parameters of the resultant glass. The intensity parameters of silicate glasses without alkali ions are larger than those of silicate glasses with alkali ions. The spontaneous radiation probability of the transition from 3F4 to 3H6 of glasses without alkali ions is 191.89s−1, which is larger than that of glasses with alkali ions. Moreover, the measured lifetime of the 3F4 energy level of glasses is larger too. Emission cross section results show a maximum value 3.89×10−21cm2 at 1882nm. These findings indicate that the glass in this study can be used to realize ~2μm lasers. The effect of variations in Tm2O2 concentration on the emission properties is also studied. Cross-relaxation and emission intensity enhance with increasing Tm2O3 content. However, the lifetime of the 3F4 level decreases because of concentration quenching. The influence of OH groups on the emission properties is also investigated.

Cooling rate and size effects on the medium-range structure of multicomponent oxide glasses simulated by molecular dynamics

A set of molecular dynamics simulations were performed to investigate the effect of cooling rate and system size on the medium-range structure of melt-derived multicomponent silicate glasses, represented by the quaternary 45S5 Bioglass composition. Given the significant impact of the glass degradation on applications of these materials in biomedicine and nuclear waste disposal, bulk structural features which directly affect the glass dissolution process are of particular interest. Connectivity of the silicate matrix, ion clustering and nanosegregation, distribution of ring and chain structural patterns represent critical features in this context, which can be directly extracted from the models. A key issue is represented by the effect of the computational approach on the corresponding glass models, especially in light of recent indications questioning the suitability of conventional MD approaches (that is, involving melt-and-quench of systems containing ~10(3) atoms at cooling rates of 5-10 K/ps) when applied to model these glasses. The analysis presented here compares MD models obtained with conventional and nonconventional cooling rates and system sizes, highlighting the trend and range of convergence of specific structural features in the medium range. The present results show that time-consuming computational approaches involving much lower cooling rates and/or significantly larger system sizes are in most cases not necessary in order to obtain a reliable description of the medium-range structure of multicomponent glasses. We identify the convergence range for specific properties and use them to discuss models of several glass compositions for which a possible influence of cooling-rate or size effects had been previously hypothesized. The trends highlighted here represent an important reference to obtain reliable models of multicomponent glasses and extract converged medium-range structural features which affect the glass degradation and thus their application in different fields. In addition, as a first application of the present findings, the fully converged structure of the 45S5 glass was further analyzed to shed new light on several dissolution-related features whose interpretation has been rather controversial in the past.

Dielectric and Spectroscopic properties of CuO doped multi-component Li2O[sbnd]PbO[sbnd]B2O3[sbnd]SiO2[sbnd]Bi2O3[sbnd]Al2O3 glass system

Multi-component silicate glasses of the chemical composition 19.4Li2O20PbO20B2O330SiO2 (10−x) Bi2O30.6 CuO: x Al2O3 with x ranging from 0 to 5mol% have been synthesized.A variety of spectroscopic (optical absorption, IR, Raman and ESR) and dielectric properties (over a range of frequency and temperature) of these glasses have been investigated as a function of Al2O3 concentration. The results of optical absorption and ESR spectral studies have indicated that a part of copper ions do exist in Cu+ state in addition to Cu2+ state especially in the samples containing low concentration of Al2O3. The IR and Raman spectral studies have revealed that there is a decreasing degree of disorder in the glass network with increase in the concentration of Al2O3 upto 3.0mol%. The values of dielectric parameters viz., dielectric constant, loss and ac conductivity at any frequency and temperature are observed to decrease as the concentration of Al2O3 is increased up to 3.0mol%. Such changes have been attributed to increase of redox ratio or increasing proportions of Cu+ ions that take part in the glass network with CuO4 structural units The quantitative analysis of the results of ac conductivity and dielectric properties have indicated a decrease in the insulating character of the glasses when the concentration of Al2O3 is raised beyond 3.0mol% in the glass network. This has been attributed to adaption of aluminium ions from tetrahedral co-ordination to octahedral co-ordination and also due to declustering influence of copper ions by aluminium ions in the glass network.

Microstructural evolution in two alkali multicomponent silicate glasses as a result of long-term exposure to solid oxide fuel cell environments

The microstructural evolution in two potential solid oxide fuel cell (SOFC) sealing glass materials exposed to air and a gas mixture of steam + H2 + N2 at 800 °C up to 10000 h was determined. The glass exposures were performed on common SOFC substrates like alumina and zirconia. Characterization of the crystalline phases and pore size distribution was performed for the specimens with various exposure conditions. Comparison of the microstructural and chemical stability of the two glasses was performed based on known trends related to glass chemistry. It was observed that multicomponent glasses followed few rules for chemical and microstructural stability reported in the literature for glasses with fewer components. The two glasses examined in this study displayed adequate resistance to devitrification but marginal resistance to porosity changes in the SOFC environment exposure. The implications of the results for the design and long-term performance of SOFC seals are discussed.

Competitive Dissolution Mechanism of Sulfur in CaMnSilicate Melts: Structural View

AbstractThe sulfide capacities of the CaOSiO2MnO(Al2O3MgO) slags were measured at 1873 K over a wide composition range using a gas‐slag equilibration method. The effects of MnO content and the MnO ↔ CaO substitution on the sulfide capacity of molten slag were also investigated based on the structural view of silicate melts. In the multicomponent silicate melts containing high MnO (up to about 50 wt%), the sulfide capacity mainly increased with increasing MnO content. Also, the sulfide capacity and the activity of MnO showed a linear relationship with a slope of unity, indicating that MnO is dominant component controlling the sulfur dissolution behavior into CaMnsilicate melts. The sulfide capacity increased as MnO substituted for CaO in the high silica melts (>30 (±5) wt% SiO2), whereas it decreased by increasing the MnO/CaO ratio in the low silica melts (<30(±5) wt% SiO2). This tendency of sulfide capacity resulted in the clock‐wisely rotating iso‐capacity contours from MnO‐free side to MnO‐rich corner in CaMnsilicate melts. The dissolution mechanism of sulfur in CaMnsilicate melts can be explained by the “Competitive dissolution mechanism.”

Modeling the viscosity of silicate melts containing manganese oxide

Our recently developed model for the viscosity of silicate melts is applied to describe and predict the viscosities of oxide melts containing manganese oxide. The model requires three pairs of adjustable parameters that describe the viscosities in three systems: pure MnO, MnO-SiO2 and MnO-Al2O3-SiO2. The viscosity of other ternary and multicomponent silicate melts containing MnO is then predicted by the model without any additional adjustable model parameters. Experimental viscosity data are reviewed for melts formed by MnO with SiO2, Al2O3, CaO, MgO, PbO, Na2O and K2O. The deviation of the available experimental data from the viscosities predicted by the model is shown to be within experimental error limits.

고상 NMR을 이용한 비정질 알루미나의 상전이 연구: 마그마 바다 구성 용융체의 결정화 과정의 의의

In order to have better insights into the chemical differentiation of Earth from its magma ocean phase to the current stratified structure, detailed information of crystallization kinetics of silicate melts consisting of the magma ocean is essential. The structural transitions in oxide glasses and melts upon crystallization provide improved prospects for a systematic and quantitative understanding of the crystallization processes. Here, we report the 3QMAS NMR spectra for sol-gel synthesized glass with varying temperature and annealing time. The NMR spectra for the amorphous show well-resolved Al coordination environments, characterized with mostly and a minor fraction of . The fraction of in the alumina phase decreases with increasing annealing time at constant temperature. The NMR results of phases also imply that multiple processes (e.g., crystallization and/or changes in structural disorder within glasses) could involve upon its phase transition. The current results and method can be useful to understand crystallization kinetics of diverse natural and multi-component silicate glasses and melts. The potential result may yield atomic-level understanding of Earth`s chemical evolution and differentiation from the magma ocean.

Modeling of the induced refractive index kinetics in photo-thermo-refractive glass

Photo-thermo-refractive (PTR) glass is a photosensitive multi-component silicate glass that exhibits refractive index change after successive UV-exposure and thermal treatment. The refractive index change was demonstrated to be associated with the precipitation of NaF nano-crystals in the glass matrix. This paper presents a systematic study of the dependence of the refractive index change on dosage of UV-exposure and thermal treatment duration and temperature in already UV-exposed and nucleated samples. It is shown using Avrami plots that the refractive index change in PTR glass is determined by a diffusion-controlled growth of particles from pre-existing nuclei while all coefficients have exponential dependence on temperature (Boltzmann law). The developed model, which includes both photo-chemistry and crystallization processes, allow describing the refractive index change dependence on dosage for a wide range of thermal treatment duration and temperature and an accuracy better than 10%.

Multicomponent Silicate Cathode Materials for Rechargeable Li-Ion Batteries: An Ab Initio Study

A first principles investigation is performed to study the structural and electrochemical properties of new multicomponent silicate materials that can be suitable for the cathode of rechargeable Li-ion batteries. The distribution of different transition metals in the silicate structure alters the structural and electronic properties of the crystal, affecting its kinetics, redox potentials and both ionic and electronic conductivities. We also explain the effect of the multiple interactions between Li ions and the transition metals. These multicomponent structures represent a very powerful strategy to control the electrochemical performance of the silicates. In this work, we finally address the implications of such strategy on the design of Li-ion batteries.

Thermodynamic Prediction of Spinodal Decomposition in Multi-component Silicate Glass for Design of Functional Porous Glass Materials

AbstractThe authors have investigated metastable phase separation in multi-component silicate glass for the fabrication of porous glass from multi-component slag. Spinodal decomposition forms an interconnected microstructure in glass spontaneously, and porous glass is obtained by leaching one of the decomposed phases with an acid solution. This porous glass can be used for a filter to remove impurities in polluted water or air. In this study, the metastable miscibility gap was predicted in multi-component silicate glass using thermodynamic analyses where glass was regarded as a super-cooled liquid phase. Occurrence of spinodal decomposition was observed in annealed glass, and it corresponded to the predicted miscibility gap. Then, we fabricated porous glass using spinodal decomposition in multi-component borosilicate glass and by removing one of the decomposed phases. Furthermore, for the creation of functional porous glass applicable for environmental purification, the spinodal decomposition was prepared in multi-component borosilicate glass containing titanium oxide based on the predicted metastable miscibility gap in multi-component silicate glass.

Non-isothermal sinter-crystallization of jagged Li2O–Al2O3–SiO2 glass and simulation using a modified form of the Clusters model

We have tested a modified form of the Clusters model of sintering for the complex case of non-isothermal sintering with concurrent crystallization of a multicomponent lithium aluminum silicate (LAS) glass having a broad size distribution of jagged particles. We compared experimental and simulated densification data using a constant heating rate. Only one adjustable parameter was used: the particle shape factor (Ks). We discuss the results in light of some complicating factors, such as temperature gradients within the powder compacts and compositional shifts of the residual glass matrix due to crystallization, which lead to changes of viscosity. The modified Clusters model accurately predicted the temperature dependence of densification and the final (saturation) density of the glass particle compacts.