Specific features of halogen binding in binary alkali silicate glasses

This paper reports on the results of the chemical synthesis of halogen-containing alkali silicate glasses M ₂O-MHal-SiO₂(M= Li, Na, K; Hal = Cl, F). From analyzing the obtained results, a conclusion is drawn regarding the specific features revealed in the incorporation of halogens into the silicate matrix. A model explaining the considerable losses of chlorides upon their introduction into binary melts is proposed.     

Kinetics of photoinduced recombination of hole-type color centers in silicate glasses

The photobleaching of the absorption band associated with the hole-type centers in a gamma-irradiated glass of the K₂O-PbO-SiO₂ system is investigated by photometry. The results obtained are compared with the data available in the literature for glasses in the Na₂O-CaO-SiO₂ system. As the exposure time increases, the optical density at the maximum of the absorption band attributed to the hole-type centers decreases according to an exponential law with a fractional exponent, which depends on the composition of the glass matrix and on the experimental conditions. This dependence is characteristic of so-called retarded bimolecular reactions. The inference is made that the retardation of the photoreaction is caused by the effect of the energy of absorbed photons on the local environment of the centers.     

AC electric field‐induced softening of alkali silicate glasses

Electric field‐induced softening (EFIS) is a recently discovered phenomenon leading to significant reduction in the furnace temperature at which glass softens under the application of DC voltage. Unfortunately, it is accompanied by local compositional changes due to migration of ions that could limit its usefulness. To overcome this drawback, we have investigated the same phenomenon using AC voltage, that is, AC‐EFIS on a sodium disilicate glass and a 50/50 mixed lithium‐sodium disilicate glass of very different ionic resistivity yet similar network structure. The results show that the magnitude of EFIS temperature reduction is significantly greater for AC compared to DC for both glass compositions. The enhancement of EFIS under AC voltage appears to be due to a more uniform power dissipation and self‐healing of changes than under DC voltage. This uniformity allows for the overall sample temperature to increase throughout the bulk and provides a better technique for practical applications than the DC case which produces potentially undesirable changes, especially in the anode region.     

Luminescence properties of Dy3+-doped alkali lead alumino borosilicate glasses

A new series of Dy³⁺-doped sodium lead alumino borosilicate glasses are prepared by the melt quenching technique with the chemical composition 20Na₂O- 10PbO-(5-x)Al₂O₃-40B₂O₃–25SiO₂-xDy2O3 (where x?=?0, 0.5, 1.0 and 1.5?mol%) and are characterized by various spectroscopic techniques such as XRD, FT-IR, Optical absorption spectra, Fluorescence spectra and Decay measurements. Optical and Luminescence spectra of all the glasses are recorded at room temperature. From the optical absorption spectra, optical band gap and Urbach energies of Dy³⁺-doped titled glasses have been evaluated. The oscillator strengths and the intensity parameters, Ω_λ (λ?=?2, 4 and 6) are calculated using Judd-Ofelt analysis. The various lasing parameters like transition probability (A_T), branching ratio (β_R), stimulated emission cross-section (σ_e) and the radiative lifetime (τ_rad) for different emission levels of Dy³⁺ ions have been evaluated. Fluorescence spectra show sharp emission peaks are observed at 482?nm (blue), 575?nm (yellow) and 665 (red) under 385?nm excitation, which are attributed to ⁴F_9/2→⁶H_15/2, ⁶H_13/2 and ⁶H_11/2 transitions respectively. The yellow-to-blue intensity ratio (Y/B) increase up to 1.0?mol% Dy³⁺ ion content and beyond it decreases because of concentration quenching which occurs due to the energy transfer between Dy³⁺ and Dy³⁺ ions. The x, y coordinates of the prepared glasses pass through the white light region in the CIE 1931 chromaticity diagram. The results reveal that these glasses emit quality white light which is suitable for the development of W-LEDs. The color purity and the correlated color temperature (CCT) are also calculated for the present work. Various physical parameters such as density, refractive index, and ion concentration etc., are calculated. Among the prepared glasses, NPABSDy10 glass exhibits higher σ_e, β_R, σ_exτ_R, and σ_exΔλ_eff values corresponding to the ⁴F_9/2→⁶H_13/2 emission band and these are in turn specifies its suitability for W-LEDs and visible laser applications.     

Luminescence and laser action of coumarin dyes doped in silicate and aluminosilicate glasses prepared by the sol-gel technique

Coumarin dyes are encapsulated in silicate and aluminosilicate polymeric glasses synthesized by the sol-gel technique. The coumarin dyes retain their luminescent properties in all of the aged gels and in many of the dried gels (xerogels). The luminescence spectra of the new optical materials are reported. The luminescence of coumarin 4 provides a probe at the molecular level of the changes which occur during the gelation and drying. The spectral changes are studied and discussed in detail. Gels and xerogels doped with coumarin 460, 480, and 540A exhibit optical gain and laser action. The laser properties of these new solid-state dye laser materials are reported and discussed.     

Enthalpies of mixing of two alkali glasses and glasses containing alkali and alkaline-earth cations

The enthalpy of mixing of silicate glasses containing Na, K, and Ba cations is estimated using differential thermal analysis. It is shown that the interaction of sodium silicate and potassium silicate glasses with barium silicate glass is an endothermic process, whereas the interaction of sodium silicate glass with potassium silicate glass is an exothermic process.     

Spectrophotometric determination of molecular forms of silica in solution during the leaching of alkali borosilicate glasses

The extraction kinetics of the components of single-phase alkali borosilicate glasses in 0.1 M HC1 solution at 26°C is investigated. Particular attention is focused on the structurization of silica. The experimental technique is based on the spectrophotometric determination of silica from the rate of formation of β-silicomolybdic heteropoly acid in the unreduced form. The computational model employed gives an insight into the kinetics of silica structurization under experimental conditions and makes it possible to determine the contributions from different molecular forms of silica to the total amount. The solution of this problem is extremely important for revealing the physicochemical features of the interaction between alkali borosilicate glasses and acid solutions.     

Spectrophotometric determination of molecular forms of silica in solution during the leaching of alkali borosilicate glasses

The extraction kinetics of the components of single-phase alkali borosilicate glasses in 0.1 M HC1 solution at 26°C is investigated. Particular attention is focused on the structurization of silica. The experimental technique is based on the spectrophotometric determination of silica from the rate of formation of β-silicomolybdic heteropoly acid in the unreduced form. The computational model employed gives an insight into the kinetics of silica structurization under experimental conditions and makes it possible to determine the contributions from different molecular forms of silica to the total amount. The solution of this problem is extremely important for revealing the physicochemical features of the interaction between alkali borosilicate glasses and acid solutions.     

Crystallization kinetics of sodium-niobium silicate glasses

The crystallization of glasses in the Na₂O-Nb₂O₅-SiO₂ system in the temperature range 690–750°C is investigated by measuring the material density and X-ray powder diffraction analysis. It is found that the kinetics of precipitation of the NaNbO₃ crystalline phase can be described by the Avrami equation with the Avrami exponentn ≈ 1. The model describing the crystallization kinetics is proposed. The crystallization of amorphous inhomogeneity regions, which are formed as a result of phase separation, is considered in the model. The consideration refers to the crystallization process governed by the nucleation of crystals in these regions. The calculated Avrami exponents are close to unity. The proposed model does not contradict the available data on the X-ray small-angle scattering that have been obtained upon crystallization of the samples and qualitatively explains a nonmonotonic variation in the material transparency during crystallization.     

Crystallization kinetics of sodium-niobium silicate glasses

The crystallization of glasses in the Na₂O-Nb₂O₅-SiO₂ system in the temperature range 690–750°C is investigated by measuring the material density and X-ray powder diffraction analysis. It is found that the kinetics of precipitation of the NaNbO₃ crystalline phase can be described by the Avrami equation with the Avrami exponentn ≈ 1. The model describing the crystallization kinetics is proposed. The crystallization of amorphous inhomogeneity regions, which are formed as a result of phase separation, is considered in the model. The consideration refers to the crystallization process governed by the nucleation of crystals in these regions. The calculated Avrami exponents are close to unity. The proposed model does not contradict the available data on the X-ray small-angle scattering that have been obtained upon crystallization of the samples and qualitatively explains a nonmonotonic variation in the material transparency during crystallization.     

Hydrogen-containing groups in silica glasses

The structures formed by hydrogen in two types of silica glass are investigated using infrared spectroscopy, ¹H magic angle spinning magnetic resonance spectroscopy, and quadrupole mass spectrometry. The results obtained from these investigations show that hydrogen in silica glass can exist in the form of isolated SiOH groups, SiOH groups with hydrogen bonds, pairs of neighboring SiOH groups, SiH groups, physically dissolved molecular hydrogen, and molecular water. The structures containing H atoms in the glass synthesized by oxygen-hydrogen gas-flame hydrolysis of SiCl₄ differ from those in the glass produced by melting a silica powder in a hydrogen atmosphere.