WO3 TeO2 Glasses Research Articles

Impact of AgNPs on the optical thermometry and stability of bismuth modified tellurium-tungstate upconverting glass

Bismuth modified Er3+/Yb3+: TeO2-WO3 (TWBi) glass system containing silver metallic nanoparticles have been synthesized via melt-quenching method. Optical absorption spectra have been used for optical bandgap and Judd-Ofelt analysis. Judd-Ofelt intensity parameters show ionic type of bonding between the activator and ligand ions. The HR-TEM analysis of the glass containing silver confirms the presence of silver metallic nano-particles (AgNPs) with average particle size ∼ 42 nm at 30 h heat-treatment. The improvement observed in the UC emission intensity of Er3+ ions has been elucidated by considering the energy transfer processes and crystal field modification. Temperature sensing ability and luminescence stability of Er3+/Yb3+: TWBi glass have been explored with and without the incorporation of AgNPs. It has been found that the upconverting glass with AgNPs have high absolute sensitivity, relative sensitivity and luminescence stability with respect to temperature as compared to the upconverting glass without AgNPs.

Enhancement of linear optical and dielectric properties as well as gamma-ray protection capacities of PbO reinforced in TeO2–WO3 glasses: Comparative study

Enhancement of linear optical and dielectric properties as well as gamma-ray protection capacities of PbO reinforced in TeO2–WO3 glasses: Comparative study

Effect of Nd3+ ions on radiation attenuation properties of PbF2–TeO2–WO3 glass system for shielding applications

This study aims to investigate the utility of using 15PbF2–(60x)TeO2–25WO3–xNd2O3 (0.1≥x≥1.5) glasses in the nuclear shielding applications for mixed radiation fields at energies ranging from 15keV to 15MeV. The effect of Nd3+ ions on gamma attenuation properties of the present glass system was discussed in detail. The radiation attenuation features were investigated for the present glass system by using Monte Carlo radiation transport simulation via Geant4 toolkit. The simulation results were theoretically approved by using Phy-X approach over the entire considered energy range. The obtained results indicate that the values of Zeff and Neff were both highest in the in the τ/ρ dominated energies due to the atomic number dependence of the cross sections of the τ/ρ absorption processes. Moreover, FNRCS values were 0.1152, 0.1152, 0.1153, and 0.1153cm−1 for PWTN1, PWTN2, PWTN3, and PWTN4 respectively. Finally, an extensive comparative study is also presented between the studied glass system and standard traditional shielding materials. The study suggests PWTN4 is the best photon shield amongst the studied PWTN-glasses.

Theoretical insights of ultrasonic relaxation in PbW-tellurite glasses

Theoretical insights of the ultrasonic relaxation process in PbO–WO3–TeO2 glasses were investigated according to a model related to the propagation of ultrasonic waves in active two-well potential. The energy transfer of the ultrasonic waves either longitudinal or transverse to the glass network can create two-well potential based on the oxygen atoms displacements. The parameters of the model such as the mutual potential energy, the loss-centers, the prolongation or shrinkage of the double-well system, deformation potential were affected with the concentrations of the PbO. The number of loss centers was correlated to the compositional dependence of the elastic moduli on PbO content. The results showed that the degree of prolongation or shrinkage of the double-well system is affected with the concentration of PbO.

Effect of ZnF2 and WO3 on elastic properties of oxyfluoride tellurite ZnF2–WO3–TeO2glasses: Theoretical analysis

The elastic properties of oxyfluoride tellurite glasses in the ternary system ZnF2-WO3 -TeO2 were analyzed and their changes when ZnF2 was replaced with TeO2 or WO3 were predicted. The most significant structural and compositional parameters were evaluated on the basis of the well known models and approaches existing in the field and correlated with both elastic moduli and Poisson's ratio. It has been found that the molar volume, fractal bond connectivity, first-order stretching force constant of the Te–O and W–O covalent bonds and dissociation energy per unit volume of the constituent components play an important role in determining and predicting of elastic moduli. The semi-empirical formula of Abd El-Moneim and Alfifi, which correlates bulk modulus with the ratio between packing density and mean atomic volume, appears to be valid for the investigated oxyfluoride tellurite glasses. On the basis of Makishima-Mackenzie's theory, the agreement between the theoretically calculated and experimentally measured values is excellent for shear and Young's moduli and satisfactory for Poisson's ratio as well as bulk and longitudinal moduli. The slight divergence between the theoretical and experimental values was interpreted in terms of the basic structural units that constituting the glass network.

Effect of the Addition of Pb3O4 and TiO2 on the Optical Properties of Er3+/Yb3+:TeO2-WO3 Glasses.

Heavy metal oxide tungstate-based tellurite glasses TeO2–WO3 (TW) containing Er3+/Yb3+ ions have been prepared by the melting and quenching method. The optical absorption and upconversion (UC) emission studies for the doped/codoped glasses have been performed. The effect of the addition of Pb3O4 and TiO2 to the Er3+/Yb3+:TW glass on its physical properties, optical absorption, and UC emission spectra under 980 nm/808 nm excitations has been studied. A significant enhancement in the UC emission intensity lying in the green and red region has been observed on introducing Pb3O4 and TiO2 into the Er3+/Yb3+:TW glass. The improvement in the UC emission intensity and full width at half maximum of the bands have been explained on the basis of energy transfer, local field correction factor, and Urbach energy. The non-color tunability in the color emitted from the prepared Er3+/Yb3+:TWPTi glass upon near-infrared (NIR) excitation at different pump power has been reported. Also, the color-correlated temperature and color purity have been measured under both NIR excitations.

Structural analysis of WO3-TeO2 glasses by neutron, high energy X-ray diffraction, reverse Monte Carlo simulations and XANES

The structure of WO3-TeO2 glasses containing 15, 20 and 25 mol% WO3 are studied by neutron diffraction (ND), high energy X-ray diffraction (XRD) and X-ray Absorption Near Edge spectroscopy (XANES). The short-range structural properties of glasses i.e. TeO and WO speciation, coordination number distributions, bond-lengths, and the OTeO, OWO and OOO bond angle distributions in the glass network are determined by the Reverse Monte Carlo (RMC) simulations of the ND and XRD data. RMC technique successfully determined all partial pair correlation functions and the coordination number distributions revealed that glass network consists predominantly of TeO4 and WO4 units with small amounts of triangular, penta and hexa co-ordinated units. The average WO and TeO bond lengths are in the ranges: 1.69–1.75 ± 0.01 Å and 1.99–2.00 ± 0.01 Å respectively. Both WO and TeO correlation peaks are asymmetrical, that indicate a distribution of their bond lengths in the respective structural units. The O-Te-O bond angle distribution has a peak at 107 ± 2°. Similarly the O-W-O bond angle distribution has a peak at 108 ± 5°. On increasing the WO3 concentration from 15 to 25 mol%, the average TeO coordination number decreases from 3.80 to 3.61 ± 0.02 due to the structural transformation: TeO4 → TeO3, similarly the WO coordination also decreases and is in the range: 3.79–3.67 ± 0.02. XANES studies found that the oxidation state of Te and W ions in the glasses are 4+ and 6+ respectively.

Photon upconversion in Ho3+-Yb3+ embedded tungsten tellurite glass

This article reports on the frequency upconversion property of yellow light emitting Ho3+-Yb3+ embedded tungsten tellurite (TeO2-WO3) glass prepared by the famous melt-quench technique. Holmium activated TeO2-WO3 glass gives efficient visible and near-infrared upconversion luminescence upon 980nm excitation, which improved via the incorporation of Yb3+ ions. The upconversion process was examined by a pump power dependence study that revealed the involvement of a single photon for upconversion emission around 886nm whereas two pump photons needed for the other emissions. The observed single and/or two photon upconversion feature is discussed with the help of a luminescence decay study and energy level diagram of the embedded ions.

Evaluation of physical, structural properties and shielding parameters for K2O–WO3–TeO2 glasses for gamma ray shielding applications

In the present work, a series of ternary glasses in the K2O–WO3–TeO2 system have been synthesized by conventional melt quenching technique. Glass formation range of the selected glass system was determined and physical, structural and radiation shielding properties of the glasses were investigated. Density (ρ), molar volume (VM), oxygen molar volume (VO), oxygen packing density (OPD), average cross-link density (nc¯), the number of bonds per unit volume (nb) and Poisson's ratio (μcal) values were evaluated for the interpretation of physical and structural properties. Fourier transform infrared (FTIR) spectra of the glasses were analyzed in order to obtain the information on the structural transformations in the glass network following the equimolar substitution of TeO2 by K2O + WO3 and changing K2O or WO3 at constant TeO2. Increasing K2O at constant TeO2 decreases the network connectivity due to the formation of non-bridging oxygen sites and the glass network became less tightly packed. On the other hand, equimolar substitution of TeO2 with WO3+K2O in these glasses resulted in a more compact glass network. The mass attenuation coefficients have been computed using WinXCom program and the obtained values were used to calculate the half value layer, the effective atomic number and the electron density. In addition, the macroscopic effective removal cross-section for fast neutron values are also evaluated. The variation of shielding parameters was discussed for WO3 variation in the glass composition and photon energy. From the derived results, it was found that K30W60T10 is the best glass in terms of shielding effectiveness among all the studied glasses due to higher values for mass attenuation coefficient, effective atomic number, and electron density and lower values of half value layer. These glasses show potentiality to be used as shielding materials and for an improved shielding effectiveness of the K2O–WO3–TeO2 glasses, a large WO3 content would be required.

Radiation shielding competence of newly developed TeO2-WO3 glasses

Gamma rays shielding effectiveness of newly developed Tellurium oxide based-glasses have been investigated. We have used Geometric Progression (G-P) fitting method for calculating the absorption (EABF) and exposure (EBF) buildup factors at energies 0.015–15 MeV. The buildup factors were found to depend strongly on the photon energy and mean free path (mfp). The EABF and EBF indicated that these types of glasses are suitable for shielding effectiveness and becoming more superior as the molar fraction of WO3 is increased in the glass compound. The present work should be useful for a possible utilizing of these glasses for optical and medical applications where radiation exposure is present.

Enhanced upconversion and temperature sensing study of Er3+–Yb3+ codoped tungsten–tellurite glass

This article reports on the visible upconversion and temperature sensing behaviour of Er3+–Yb3+ doped/codoped TeO2–WO3 glasses prepared by a melting and quenching method. The upconversion emissions have been observed throughout the visible and infrared region upon 980nm and 808nm excitations and assigned suitably from different transitions of the Er3+ ion. The emission intensities of the most intense green band have been enhanced on the co-doping with theYb3+ ions with about 5.92 and 3.99 times upon 980 and 808nm excitations, respectively. The reason behind this improvement is explained on the basis of a power dependence study and an energy level structure. The colour tunability behaviour of the codoped glass has also been investigated upon both excitations. The temperature sensing performance of the prepared glass has been studied by using the fluorescence intensity ratio technique up to 745K. The results suggested that the present glass is a suitable candidate for making a high temperature sensor up to 690K with a sensitivity of about 28.72×10−4K−1.

Fabrication of optical channel waveguides in crystals and glasses using macro- and micro ion beams

Active and passive optical waveguides are fundamental elements in modern telecommunications systems. A great number of optical crystals and glasses were identified and are used as good optoelectronic materials. However, fabrication of waveguides in some of those materials remains still a challenging task due to their susceptibility to mechanical or chemical damages during processing. Researches were initiated on ion beam fabrication of optical waveguides in tellurite glasses. Channel waveguides were written in Er:TeO2–WO3 glass through a special silicon mask using 1.5MeV N+ irradiation. This method was improved by increasing N+ energy to 3.5MeV to achieve confinement at the 1550nm wavelength, too. An alternative method, direct writing of the channel waveguides in the tellurite glass using focussed beams of 6–11MeV C3+ and C5+ and 5MeV N3+, has also been developed. Channel waveguides were fabricated in undoped eulytine-(Bi4Ge3O12) and sillenite type (Bi12GeO20) bismuth germanate crystals using both a special silicon mask and a thick SU8 photoresist mask and 3.5MeV N+ irradiation. The waveguides were studied by phase contrast and interference microscopy and micro Raman spectroscopy. Guiding properties were checked by the end fire method.

Leaky mode suppression in planar optical waveguides written in Er:TeO2–WO3 glass and CaF2 crystal via double energy implantation with MeV N+ ions

Ion implantation proved to be an universal technique for producing waveguides in most optical materials. Tellurite glasses are good hosts of rare-earth elements for the development of fibre and integrated optical amplifiers and lasers covering all the main telecommunication bands. Er3+-doped tellurite glasses are good candidates for the fabrication of broadband amplifiers in wavelength division multiplexing around 1.55μm, as they exhibit large stimulated cross sections and broad emission bandwidth. Calcium fluoride is an excellent optical material, due to its perfect optical characteristics from UV wavelengths up to near IR. It has become a promising laser host material (doped with rare earth elements). Ion implantation was also applied to optical waveguide fabrication in CaF2 and other halide crystals. In the present work first single-energy implantations at 3.5MeV at various fluences were applied. Waveguide operation up to 1.5μm was observed in Er:Te glass, and up to 980nm in CaF2. Then double-energy implantations at a fixed upper energy of 3.5MeV and lower energies between 2.5 and 3.2MeV were performed to suppress leaky modes by increasing barrier width.

Thermal properties and crosslinking of binary TeO2–Nb2O5 and TeO2–WO3 glasses

Binary tellurite glasses in the form (100−x)TeO2–xAnOm and AnOm=Nb2O5 and WO3 oxides have been prepared by the melt quenching technique and x=4, 10mol% for Nb2O5 and 20mol% WO3. Density and molar volume have been measured and calculated. Differential scanning calorimetric curves of these glasses have been investigated to measure thermal properties of these glasses. The thermal properties were the glass transition temperature Tg (°C), the onset of crystallization temperature Tx (°C) and the glass stability S=(Tx−Tg) (°C). The glass transition temperature has been analyzed according to the average crosslink density that is present in the glass.

Optical, thermal, and structural properties of Nb2O5–TeO2 and WO3–TeO2 glasses

Glass samples from two systems, Nb2O5–TeO2 and WO3–TeO2, were prepared at two melt quenching rates and characterized by density, DSC, UV-visible, and Raman spectroscopy. Addition of Nb2O5 decreased the density while increase in the WO3 concentration increased the density. Glasses prepared at higher quenching rates had smaller densities than glasses of the same composition prepared at lower quenching rate although the short-range structure of both glasses were identical, as revealed by Raman spectroscopy. Optical studies found an intense absorption band just below the absorption edge in both the glass series. This band was attributed to electronic transitions of Nb5+ and W6+ ions and a lone pair of electrons on Te atoms. Glass transition temperature increased with increase in Nb2O5 and WO3 mol% due to the increase in average bond strength in the glass network. Raman spectroscopy showed that the concentration of TeO4 units decreased with the increase in Nb2O5 and WO3 concentrations.

Structural peculiarities and Raman spectra of TeO2/WO3-based glasses: A fresh look at the problem

Ideas currently dominating the field of structural studies of TeO2-based glasses are critically considered. A new physically and chemically consistent approach to the constitution of binary TeO2–WO3 glasses is proposed, in which the reasoning coming from the Raman spectra reexamination are correlated with the basic principles of thermodynamics. Separation into two phases is suggested in such glasses. One phase is TeO2, and another is Te(WO4)2 consisting of tetrahedral [WO4]2− anions and of Te4+ cations. Supplementary MnOk oxides added to the glasses are found incorporated in the former phase, thus producing solid solutions (for M=Ti, Nb) or tellurite compounds (for M=Nd).

Optical properties of Tm3+-doped TeO2-WO3 glasses

Tm3+-doped TeO2-WO3 glasses have been prepared and their absorption spectra have been measured in the visible to IR (up to 7 μm) spectral region. Luminescence measurements have shown that the glasses have emission bands at 1.45 and 1.8 μm. An attempt was made to remove OH groups from the glasses using KBF4 and an inert atmosphere during the glass preparation. The results demonstrate that a low OH content can be achieved only by combining these approaches. The 1.8-μm emission intensity in “dry” glass is a factor of 6 higher than that in the OH-containing glasses. The relevant Judd-Ofelt parameters have been calculated.

Structures and Third-Order Optical Nonlinearities of BiO1.5-WO3-TeO2 Glasses

We investigated third-order optical nonlinearities (χ(3)) by femto-second Z-scan technique for various compositions of bismuth–tungsten–tellurite glasses (xBiO1.5–20WO3–(80–x)TeO2; x=0–15) as well as their Raman scattering spectra. It was revealed that a small additive of BiO1.5 (5 mol%) in WO3–TeO2 glass was capable of improving a real part of χ(3). However, an excess amount of BiO1.5 decreased the nonlinearity, resulting from TeO4–to–TeO3+1 transformation with an increase in BiO1.5. We shall attempt to explain the improvement on a basis of a two-phases model for WO3–TeO2 glasses.

Infrared Spectroscopic Characterization of Tellurite Glasses Containing Heavy Metal Oxides

The infrared (IR) spectra of (100-x)TeO2–xWO3 glasses reveal that the glass network consists of [TeO3]/[TeO3+1], [TeO4], [WO4], and [WO6] groups as basic structural units. Addition of WO3 oxide to the binary TeO2–WO3 glasses increases the amount of lower coordination of [TeO3]/[TeO3+1] units and decreases the higher coordination of [TeO4] units and also the formation of Te–O–W linkages at the expense of Te–O–Te linkages. The IR spectra of 60TeO2–(40-x)WO3–xPbO glasses reveal that the glass network consists of [TeO3], [TeO4], [WO4], [WO6], and [PbO4] units. Changes in the coordination state of tellurium and tungsten ions occur when the PbO and WO3 concentrations are varied. The dual role of the lead ions is confirmed in 60TeO2–(40-x)WO3–xPbO glass system. The W ion coordination state changes from 4 to 6 when WO3 concentration increases beyond 30 mol% in both (100-x)TeO2–xWO3 and 60TeO2–(40-x)WO3–xPbO glass systems. The IR spectra of 60B2O3–10TeO2–(30-x)ZnO–xPbO glasses reveal that the glass network consists of [TeO3], [BO3], and [BO4] groups.

Structure of WO3-TeO2 glasses

WO3-TeO2 glasses have been studied by quantum-chemical simulation and Raman spectroscopy. The results have been used to develop a model for the network of tungstate-tellurite glasses. The model allows one to correlate the structure and optical properties (in particular, the position and intensity of Raman bands) of the glasses with their composition. The network of the glasses is shown to be made up, for the most part, of three types of structural groups: TeO4 trigonal dipyramids, O=TeO2 pyramids, and O=WO5 octahedra. Any other structural units, in particular, WO4 tetrahedra, are unnecessary. The model for the network of WO3-TeO2 glasses can be used to analyze the vibrational spectra of tungstate-tellurite glasses in a broad composition range. In particular, using this model we assigned the Raman spectra of the tungstate-tellurite glasses in the range 550–950 cm−1.