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We have investigated the spectroscopic properties of Er3+-doped fluorotellurite glasses with the basic molar composition 75%TeO2-10%P2O5-10%ZnO-5%PbF2, modified by replacing 5% TeO2 by a metal oxide, namely WO3 or Nb2O5. The absorption edge of the glasses studied has been described within the Urbach approach, while the absorption and photoluminescence spectra have been analyzed in terms of the standard Judd-Ofelt theory, along with the photoluminescence decay of the 4I13/2 and 4S3/2 levels of the Er3+ ion. The absorption and emission spectra of the 4I15/2 ↔ 4I13/2 infrared transition have been analyzed within the McCumber theory to yield the peak emission cross-section and figure of merit for the amplifier gain. It appears that the fluorotellurite glass containing WO3 as a modifier is characterized by the largest figure of merit, indicating this matrix as a promising new host for doping with Er3+ ions. [ABSTRACT FROM AUTHOR]

Novel glass samples with the composition 75TeO2–5Ta2O5–15Nb2O5–5x (where x = ZnO, MgO, TiO2, or Na2O) in mole percent were prepared. The physical, optical, and gamma radiation shielding properties of the glass samples were studied over a wide energy spectrum ranging between 0.015 and 20 MeV. The glasses' UV–vis spectra were utilized to evaluate the optical energy gap and refractive index. Glass samples had a refractive index ranging from 2.2005 to 2.0967. The results showed that the sample doped with zinc oxide (ZnO) recorded the highest density (ρglass), molar polarizability (αm), molar refraction (Rm), refractive index (n), and third-order nonlinear optical susceptibility (χ3) and the lowest optical energy gap (Eopt) among the samples under investigation. When comparing the current glass system with various standard glass shielding materials, the prepared glass system showed superior shielding performance at energies ranging between 40 and 85 keV. These findings indicate that the prepared glass systems can be used in diagnostic X-rays, especially in dental applications. [ABSTRACT FROM AUTHOR]

A neodymium (Nd3+) doped oxyfluoride glass ceramics containing SrF2, LaF3 nanocrystals has been presented. Transparent glass ceramics was obtained by heat treating the glass from the SiO2--Al2O3--ZnO--Na2O--SrF2 and SiO2--Al2O3--ZnF2--Na2O--LaF3 system at the first crystallization temperature. Cerammization of glass was studied by DTA/DSC, XRD. It has been found that nanocrystallization of SrF2 and LaF3 strongly depends on the ratio between the components and the amount of SrF2 and LaF3, respectively. The optical studies of the glasses comprised spectrophotometry (reflectance and transmittance) and spectroscopic ellipsometry. The spectrophotometric measurements yield a number of narrow absorption bands which correspond to characteristic transitions between the ground- and consecutive excited states of rare earth ions. Growth luminescence at typical neodymium wavelength was observed under diode laser (808 nm) excitation in glass ceramics with SrF2 in comparison to parent glass. The optimization of cerammization process allowed to fabricate the oxyfluoride glass ceramics optical fibre with strong emission originated from Nd3+ ions. The influence of the cerammization process on the changes in the refractive index of glass was examined. [ABSTRACT FROM AUTHOR]

To support commercialization of the MgO-Al2O3-B2O-SiO2-based low-dielectric glass fibers, crystallization characteristics of the relevant glasses was investigated under various heat-treatment conditions. The study focused on the effects of iron on the related thermal properties and crystallization kinetics. Both air-cooled and nucleation-treated samples were characterized by using the differential thermal analysis/differential scanning calorimeter method between room temperature and 1200°C. A collected set of properties covers glass transition temperature ( Tg), maximum crystallization temperature ( Tp), specific heat (Δ C p), enthalpy of crystallization (Δ Hcryst), and thermal stability (Δ T= Tp- Tg). Using the Kinssiger method, the activation energy of crystallization was determined. Crystalline phases in the samples having various thermal histories were determined using powder X-ray diffraction (XRD) and/or in situ high-temperature XRD method. Selective scanning electron microscope/energy-dispersive spectroscopy analysis provided evidence that crystal density in the glass is affected by the iron concentration. Glass network structures, for air-cooled and heat-treated samples, were examined using a midinfrared spectroscopic method. Combining all of the results from our study, iron in glass is believed to function as a nucleation agent enhancing crystal population density in the melt without altering a primary phase field. By comparing the XRD data of the glasses in two forms (bulk versus powder), the following conclusions can be reached. The low-dielectric glass melt in commercial operation should be resistant to crystallization above 1100°C. Microscopic amorphous phase separation, possibly a borate-enriched phase separating from the silicate-enriched continuous phase can occur only if the melt is held at temperatures below 1100°C, that is, below the glass immiscibility temperature. The study concludes that neither crystallization nor amorphous phase separation will be expected for drawing fibers between 1200°C and 1300°C in a commercial operation. [ABSTRACT FROM AUTHOR]

The influence of nanocrystallization process in oxyfluoride glasses Na2O-Al2O3-SiO2-LaF3-NaF doped with rare earth (RE) ions on their thermal and optical properties is studied. The thermal characteristics of oxyfluoride glasses (OG) with Tm3+, Yb3+ are presented. The effect of the glass crystallization on thermal stability of the glass and crystallizing phases formed upon heat treatment is investigated by DTA/DSC and XRD methods. It has been found that the effect of nanocrystallization of LaF3 and incorporation of RE elements in formed upon heat treatment nanocrystallites depends on the kind of rare earth elements and is determined by factors of crystallochemical nature and requires adequate proportions between the components forming glass structure. The ellipsometric investigations are performed by M2000 spectroscopic ellipsometer. These measurements allowed us to determine dispersion of refractive indices in the range 190-1700 nm and depolarization coefficients. The influence of nanocrystallization process on refractive indices is discussed. [ABSTRACT FROM AUTHOR]

The goal of the work was to characterize and synthesize tellurite glasses from the TeO2-WO3-PbO-La2O3 system. The effect of lanthanum oxide content on the tendency to the crystallization of glassy matrix was investigated. Differential thermal analysis DTA/DSC, XRD measurement were considered in terms of the lanthanum oxide influence. Presented work is a continuation of investigations of tellurite glasses with use of the Faraday effect method. The Faraday effect is a rotation of polarization of linearly polarized light in an isotropic transparent material under the magnetic field. It has been stated that the addition of lanthanum to tellurite glass from the TeO2- WO3-PbO system hinders the crystallization process of glass which is very important during fiber drawing. Tellurite glasses have physical and chemical properties that make this class of materials a potential candidate in different applications, such as electrochemical and optoelectronic devices. In the field of photonics these glasses may be used as precursors for infrared fibers or windows due to the possibility of changing their phonon energies and therefore the domain of wavelength transparency as a function of compositions. [ABSTRACT FROM AUTHOR]

The paper presents new glass-ceramics as a material for up-conversion luminescence. Formation of the LaF3 nanocrystals have been obtained as a low phonon host for rare earth active ions in oxide glassy matrix. The thermal conditions of LaF3 nanocrystallization in the glass from the SiO2-Al2O3-Na2O-LaF3 system have been presented. Transmittance and luminescence properties as a function of heat treatment have been investigated. The effect of incoming of Er3+ in LaF3 crystals has been shown on the luminescence properties. AFM results have confirmed the growth of nano-scale crystals. [ABSTRACT FROM AUTHOR]

Tests on glass texture were made in order to establish the size of porous space in modified glasses Al2O3 from the system Na2O-B2O3-SiO2 after extraction of dissolved boron phase during chemical treatment. A difference was observed in the size and volume of mezo- and micropores in 0.6% and 0.3% Al2O3 glasses depending on temperature of heating. Accounting for the difference of glass structure attempts were made to use them for the selective sorption of hydrocarbons dissolved in water. It follows from the obtained results that differences in hydrocarbon removal are as much as tens of percent. The efficiency of removal is conditioned by the type of glass and grain size of glass applied for sorption. [ABSTRACT FROM AUTHOR]

Abstract: The purpose of this work was to investigate the spectroscopic properties of Pr3+ ions of various concentrations embedded in a new matrix, namely a tellurite–tungstate glass with the molar composition 60%TeO2–27%WO3–10%PbO–3%La2O3 (TWPLa). The optical absorption edge of the TWPLa matrix has been described within the Urbach approach, while the absorption and fluorescence spectra of the Pr3+-doped TWPLa glasses have been analyzed in terms of the standard Judd–Ofelt (J–O) theory along with the luminescence decay of the 3P0 and 1D2 levels of the Pr3+ ion. A significant influence of the Pr3+ ion concentration on the photoluminescence intensity as well as on decrease of the lifetimes of both levels has been explained by a non-radiative energy transfer between the ions through different cross-relaxation channels. The spectroscopic studies have been completed with ellipsometric measurements providing the dispersion relation of the refractive index of the investigated glasses that has been taken into account in the J–O analysis. [Copyright &y& Elsevier]

Abstract: Multicomponent telluride-tungstate glasses containing Nd3+ and Er3+ ions were studied experimentally at 77 and 293K using spectroscopic methods. The Judd–Ofelt intensity parameters were derived from the absorption spectra and used to calculate the radiative lifetimes and branching ratios. The quantum efficiency η =0.95 of the 4F3/2 level of Nd3+ ion is higher than the typical value of other tellurite-based glasses. For low concentration of Er3+ ions, the luminescence decay of the 4S3/2 and 4I11/2 levels is governed by radiative transitions and multiphonon relaxation involving the Te-O highest energy vibrations. [Copyright &y& Elsevier]