Tellurite Glasses

The glass-forming domain and physical properties, namely, the density, thermal, structural and linear optical properties of new glasses within the TeO 2-TiO 2-WO 3 system have been investigated. By means of micro-Raman spectroscopy, the structure of these glasses was examined based on a full-scale spectral decomposition. The optical transmission and refractive index dispersion were measured by UV–Vis-NIR spectroscopy and spectro-scopic ellipsometry respectively. Consistent correlations were established between the structural and linear optical properties. Only minor structural modifications of the original TeO 2-rich network are taking place upon adding TiO 2 or WO 3 , suggesting the absence of Te–O–Te bond network depolymerization. Our results also suggest that, upon increasing TiO 2 content, a phase separation occurs between amorphous TeO 2-rich and amorphous TiO 2-rich regions. We also argue that the structural trends upon adding WO 3 evolve from uniformly dispersed WO 6 octahedra (at low WO 3 content) to amorphous WO 3-like regions (at higher WO 3 content) before the crystallization of γ-WO 3 at 30 mol% of WO 3. The compositional dependence of the refractive index and several optical constants (Urbach E U and dispersion E d energies, oxide ion polarizabilities) is highlighted. These glasses collectively exhibit high refractive indices in the order of ~2.2.

A B S T R A C T BaO-TeO 2 glasses containing 10 to 20-mol% BaO were studied by X-ray diffraction, density, thermal analysis, UV–visible and Raman spectroscopy. The effects of Eu 3 + , Dy 3 + , Er 3 + and Nd 3 + on the density, thermal, optical absorption and luminescent properties of barium tellurite glasses were studied. The short-range structure of barium tellurite glasses consists of TeO 4 trigonal bipyramidal and TeO 3 trigonal pyramidal units. TeeO coordination (N TeeO) was determined by Raman studies; it was found that that N TeeO decreases with increase in BaO and rare earth oxide concentration. The glass transition temperature is a function of both the average single bond enthalpy and non-bridging oxygen concentration in the glass network. Glasses containing Dy 3 + and Eu 3 + show strong visible light photoluminescence, and our results show that barium tellurite glasses are suitable hosts for rare earth ion luminescence due to low phonon energies.

The effects of addition of Al3+, W6+, Nb5+ and Pb2+ on the density, thermal, optical properties of borotellurite glasses and on the B-O, Te-O and Al-O speciation are studied. Density maximizes in glasses containing Pb2+ and minimizes in glasses with Al3+. The optical absorption cutoff wavelength increases with the addition of heavy metal ions while Al3+ shifts it to lower wavelengths. W6+, Nb5+ and Al3+ strengthen the borotellurite network and enhance the glass transition temperatures, however Pb2+ decreases it. The glass transition temperature is a linear function of the average single bond energy of the glass network. 11B Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) and Fourier Transform Infrared studies found that the BO4 structural units are unstable in the presence of Al3+, W6+ and Nb5+, however Pb2+ have an opposite effect and promote the formation of BO4. 27Al MAS NMR showed that alumino-borotellurite glasses contain AlO6, AlO5 and AlO4 structural units whose relative concentrations depend on alumina mol. %. Raman spectroscopy was used to determine Te-O coordination in glasses, the later decreased on adding metal ions and Al3+ produced a maximum suppression of TeO4 units.

A B S T R A C T Glass and anti-glass samples of Bi 2 O 3-TeO 2 and Bi 2 O 3-Nb 2 O 5-TeO 2 were prepared by ice-water quenching and normal-quenching respectively. The bismuth tellurite system has poor glass forming ability (GFA) and forms a glassy phase at low Bi 2 O 3 concentration of 2 to 5-mol%. On increasing Bi 2 O 3 concentration to 10 mol%, a mixture of glass and anti-glass phases are formed by rapid quenching of the melt. A further increase in Bi 2 O 3 concentration to 20 mol%, produces a sample consisting of entirely Bi 2 Te 4 O 11 anti-glass upon melt-quenching. An anti-glass is a solid, which has long range order of cations (Te 4+ , Bi 3+ , Nb 5+ etc.) but these are statistically distributed at their sites while the anion sites are partially vacant. Consequently the X-ray diffraction (XRD) patterns of bismuth tellurite and bismuth niobium tellurite anti-glass samples show sharp XRD peaks but the Raman spectra show broad phonon bands due to disturbed short-range order of the anions. The addition of Nb 2 O 5 to the Bi 2 O 3-TeO 2 system significantly enhances the GFA. Samples from the system: xBi 2 O 3-xNb 2 O 5-(100-2x)TeO 2 grow micro-inclusions or spherulites of size of several micron within the glass matrix on slow melt-cooling. Heat treatment of 7.5Bi 2 O 3-7.5Nb 2 O 5-85TeO 2 sample show structural transitions from glass→ anti-glass →crystalline phases.

Thermal, structural and optical properties of Nd 3 + ions in tellurite glass (TeO 2 –ZnO–Na 2 O–Li 2 O–Nb 2 O 5) have been investigated. Differential thermal analysis revealed reasonably good forming tendency of the glass composition. FTIR spectra were used to analyze the functional groups present in the glass. Judd–Ofelt intensity parameters were derived from the absorption spectrum and used to calculate the radiative lifetime, branching ratio and stimulated emission cross-section of the 4 F 3/2-4 I 9/2 , 11/2, 13/2 transitions. The quantum efficiency of the 4 F 3/2 level is comparable as well as higher than the typical value of the other tellurite based glasses. The decay from the 4 F 3/2 level is found to be single exponential for different concentrations of Nd 3 + ions with a shortening of lifetime with increasing concentration. The experimental values of branching ratio and saturation intensity of 4 F 3/2-4 I 11/2 transition indicate the favourable lasing action with low threshold power.

Tellurite and borotellurite glasses containing Bi 2 O 3 and TiO 2 were prepared and structure-property correlations were carried out by density measurements, X-ray diffraction, Differential Scanning Calorimetry (DSC), Raman, FTIR, UV–visible and 11 B MAS-NMR studies. Titanium-tellurite and titanium bismuth tellurite glasses require high melt-cooling rates and were prepared by splat quenching. On adding B 2 O 3 , the glass forming ability (GFA) enhances considerably and bulk glasses could be synthesized at lower quenching rates. The density of glasses shows a direct correlation with molecular mass of the constituents. UV–visible studies were used to determine the optical band gap and refractive index. Raman studies found that the coordination number of tellurium ions with oxygen (N TeeO) remains constant with variation in TiO 2 molar content, while the incorporation of B 2 O 3 and Bi 2 O 3 decreases N TeeO. DSC studies show that the glass transition temperature (T g) increases with B 2 O 3 and TiO 2 concentrations and that T g correlates well with bond enthalpy of the metal oxides. 11 B MAS-NMR studies found that the coordination number of boron with oxygen (N BeO) decreases with increase in B 2 O 3 content while increasing TiO 2 and Bi 2 O 3 concentration does not significantly modify N BeO .

In the present work, multicomponent tellurite glasses were elaborated by the melt quench technique with different concentrations of Er 3 þ ions. Amorphous nature of all the glasses was confirmed using X-ray diffraction patterns. The thermal parameters, such as glass transition temperature (T g) and the onset of crystallization temperature (T X), were determined by the differential scanning calorimetry. Judd–Ofelt parameters were derived for 0.5 mol% Er 3 þ-doped glass from the absorption measurements, and in turn, used to find the radiative properties of 4 S 3/2 , 2 H 11/2 and 4 I 11/2 levels of Er 3 þ ion. A green emission corresponding to 4 S 3/2-4 I 15/2 and 2 H 11/2-4 I 15/2 transitions of Er 3 þ ions was observed in the glasses under investigation. Efficient green upconversion luminescence was observed under 976 nm excitation. The emission bands centered at 529 and 543 nm confirmed that two photons contribute to the upconversion processes. We have also analyzed the dependence of downconversion as well as upconversion as a function of Er 3 þ ion concentration, which shows quenching of photoluminescence intensity above 0.5 mol% doping. From the emission spectra, CIE color coordinates of 0.5 mol% Er 3 þ-doped glass was examined. Fluorescence decay curves for the 4 S 3/2-4 I 15/2 transition for all the doped glasses have been measured and analyzed. Absorption cross-section and calculated emission cross-section, using the McCumber method, for the 4 I 13/2 2 4 I 15/2 transitions were evaluated and discussed.

Laser direct write of silver nanoparticles from solution onto glass substrates for surface-enhanced Raman spectroscopy Appl. Phys. Lett. 91, 023107 (2007); 10.1063/1.2753090 Surface enhanced Raman scattering of p-aminothiophenol self-assembled monolayers in sandwich structure fabricated on glass

Intisari Penelitian ini mengkaji indeks bias kaca berbasis tellurite TBZP yang dipengaruhi oleh variasi PbO. Kaca TBZP difabrikasi dengan teknik melt quenching dengan komposisi 55TeO 2 –2Bi 2 O 3 –[43-x]ZnO–xPbO (%mol) dengan x= 1, 2, 3, 4, 5. Reflektansi dan indeks bias kaca diukur dengan metode sudut brewster pada mode tranverse electric (TE) dan mode tranverse magnetic (TM). Hasil penelitian menunjukkan nilai reflektansi pada mode tranverse electric terus meningkat seiring dengan meningkatnya sudut datang. Pada mode tranverse magnetic dapat ditentukan besar sudut brewster yang akan menentukan nilai indeks bias kaca. Indeks bias kaca TBZP meningkat seiring dengan meningkatnya konsentrasi PbO dalam kaca. Kata Kunci: kaca, tellurite, reflektansi, indeks bias, metode sudut brewster. Abstract This research analyzed the refractive index of tellurite-based glass TBZP affected by variations PbO. The TBZP glass has been fabricated by melt quenching technique with composition 55TeO 2-2Bi 2 O 3-[43-x] ZnO-xPbO (mol%) with x= 1, 2, 3, 4, 5. Reflectance and refractive index of glass were determided by brewster angle method on tranverse electric (TE) mode and tranverse magnetic (TM) mode. Reflectance on tranverse electric mode increase with increasing the angle of incidence. From the tranverse magnetic mode data, the brewster angle were determined and also the value of refractive index of the glass. Refractive index of TBZP glass increase with increasing concentration of PbO in the glass.

The thermal characteristics of the quaternary TeO 2 –ZnO–Na 2 O–Er 2 O 3 glass system as a function of rising Er 2 O 3 mol% have been studied from the kinetic point of view. Differential scanning calorimetry technique under non-isochronal conditions at various heating rates has been used to define the characteristic temperatures of the glasses (i.e. glass transition, crystallization) in addition to the glass stability parameters. The activation energies required for both the glass transition and amorphous to crystalline transformation have been computed by different methods. The mode of the glass crystallization has been determined in terms of the Avrami kinetic constant to identify the crystallization succession. Quantitative analysis of the thermal characteristics and kinetic parameters of the glass were achieved in terms of cross-linking density, number of bonds, and the bond stretching force.

Studies such as optical absorption, Fourier transform infrared spectroscopy (FTIR), Raman spec-troscopy, Electron paramagnetic resonance (EPR) spectroscopy and Differential scanning calorime-try (DSC) were carried out on VO 2+ ion doped TeO2-TiO2-ZnO-Nb2O5 glass system. Raman and FTIR spectra of the glasses revealed the presence of [TeO3], [TeO4] and [NbO6] structural units in the glass network. The Urbach energy (ΔE), cutoff wavelength (λc), optical band gap (Eopt), optical basicity (Λ) and electron polarizability (α) of the glasses were determined from optical absorption studies. The density (ρ), molar volume (Vm), oxygen molar volume (Vo) and refractive index (n) were also measured. Spin-Hamiltonian parameters were calculated from the EPR studies. When Nb2O5 was increased at the expense of ZnO, the density, optical band gap and Urbach energy of the glasses increased, and the electronic polarizability and optical basicity decreased. The EPR spectra clearly showed that vanadium was in the glass as VO 2+ and occupied octahedral sites with tetrahedral compression. Spin-Hamiltonian parameters g and g ⊥ decreased as Nb2O5 content increased in the glass. The glass transition temperature (Tg) also increased with increasing Nb2O5 content in the glass.

Over the years there has been numerous researches on thermal stability and other thermal parameters of glasses. Among the glasses, tellurite glasses has become more interesting but challenging lately. These properties are essential in unravelling the physical properties of the glasses. But there is not much information on thermal properties of Dysprosium doped zinc sodium tellurite glass, hence the need for this study. Therefore systematic series of quaternary zinc sodium tellurite glasses doped with dysprosium ion in the form (65-x)TeO2-25ZnO-10NaO-xDy2O3 (where x = 0.0, 0.4, 0.8, 1.2, 1.6, and 2.5 mol%) have been successfully prepared via conventional melt quenching technique. X-Ray Diffraction (XRD) pattern was used to confirm the amorphous nature of the glasses, while density (ρ) of the prepared glasses were obtained via Archimedes method. Differential thermal analysis (DTA) curves for the studied glass samples with different Dy2O3 contents have been obtained to determine the glass transition temperature (í µí±‡g), crystallization temperature (Tc), glass stability temperature (ΔTs) Hruby's parameter (H). From the DTA profile, the glass transition temperature Tg, was in the range of 287-302 °C, crystallization temperature Tc from 408-502 °C, glass melting temperature Tm, 662-659 °C and crystallization onset temperature Tx is estimated to be between 354-389 °C. The thermal stability factor, defined as ΔTs = Tc-Tg, for all the samples are higher than 100 °C while Hruby's parameter H, is 0.47-1.33. These suggest that the prepared tellurite glass exhibits a good thermal stability and consequently might be a potential candidate for fibre drawing and other nonlinear optical devices.

The structure of WO 3-TeO 2 glasses containing 15, 20 and 25 mol% WO 3 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. TeeO and WeO speciation, coordination number distributions, bond-lengths, and the OeTeeO, OeWeO and OeOeO 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 TeO 4 and WO 4 units with small amounts of triangular, penta and hexa coordinated units. The average WeO and TeeO bond lengths are in the ranges: 1.69–1.75 ± 0.01 Å and 1.99–2.00 ± 0.01 Å respectively. Both WeO and TeeO 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 WO 3 concentration from 15 to 25 mol%, the average TeeO coordination number decreases from 3.80 to 3.61 ± 0.02 due to the structural transformation: TeO 4 → TeO 3 , similarly the WeO 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.

On the basis of DTA analyses of 0.9TeO2 – 0.1GeO2 and 0.8TeO2 – 0.2GeO2 glasses, the Avrami parameters were determined to be 3 indicating that the mechanism for the crystallization is bulk crystallization. DTA analyses were carried out at different heating rates and two crystallization peaks were observed for both of the glass compositions. The crystallization activation energies were determined by using the variation of peak temperatures with the heating rate. The absorption spectra measured between 300 – 800 nm wavelength region were used to determine the optical band-gap and Urbach energies of the glasses. It is found that they both are a function of glass composition.

A B S T R A C T Alumino-tellurite glasses with wide range of Al 2 O 3 concentration (1 to 20-mol%) are prepared and their short-range structural and thermal properties are studied by Raman spectroscopy, 27 Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) and Differential Scanning Calorimetry (DSC). Glass sample with 1-mol% of Al 2 O 3 has TeeO coordination of 3.66, which is close to the value of 3.68 reported in pure TeO 2 glass. TeeO coordination decreases steadily to 3.33 on increasing alumina content to 20-mol%. 27 Al MAS-NMR studies found that Al ions exist in hexa, penta and tetrahedral coordination in the alumino-tellurite network. On increasing alumina content from 3 to 20-mol%, the concentration of hexa-coordinated AleO units decreases from 54% to 35% with a simultaneous increase in the concentration of penta and tetra coordinated AleO units. Glass transition temperature increases with increase in Al 2 O 3 concentration and correlates directly with the average single bond enthalpy of the glass network.

A B S T R A C T A series of Gd 2 O 3 doped sodium zinc tellurite [xGd 2 O 3-(0.8-x) TeO 2 −0.1Na 2 O-0.1ZnO] glasses are prepared by the conventional melt quenching method and their optical properties have been studied. UV–vis spectro-photometric studies within the wavelength range from 230 nm–800 nm are carried out in the integrating sphere mode to study the effect of Gd 2 O 3 doping on the optical band gap (E g), refractive index (n), dielectric constant (ε r) and susceptibility (χ). Other physical properties like molar volume, molar refraction, polarizability, metallization criterion, number density of rare-earth ions (N), polaron radius (r p), inter ionic distance (r i), molar cation polarizability (∑α i), number of oxide ions in chemical composition (N O2-), optical band gap based electronic oxide ion polarizability (α O2-) and optical basicity (Λ) of glass samples have been studied on the basis of UV–vis spectra and density profile of the different glasses.

Tellurite and borotellurite glasses containing Bi 2 O 3 and TiO 2 were prepared and structure-property correlations were carried out by density measurements, X-ray diffraction, Differential Scanning Calorimetry (DSC), Raman, FTIR, UV–visible and 11 B MAS-NMR studies. Titanium-tellurite and titanium bismuth tellurite glasses require high melt-cooling rates and were prepared by splat quenching. On adding B 2 O 3 , the glass forming ability (GFA) enhances considerably and bulk glasses could be synthesized at lower quenching rates. The density of glasses shows a direct correlation with molecular mass of the constituents. UV–visible studies were used to determine the optical band gap and refractive index. Raman studies found that the coordination number of tellurium ions with oxygen (N TeeO) remains constant with variation in TiO 2 molar content, while the incorporation of B 2 O 3 and Bi 2 O 3 decreases N TeeO. DSC studies show that the glass transition temperature (T g) increases with B 2 O 3 and TiO 2 concentrations and that T g correlates well with bond enthalpy of the metal oxides. 11 B MAS-NMR studies found that the coordination number of boron with oxygen (N BeO) decreases with increase in B 2 O 3 content while increasing TiO 2 and Bi 2 O 3 concentration does not significantly modify N BeO .

Raman, IR and DSC studies have been carried on the (100−x)TeO2–xWO3 (TW) glasses with 10 ≤ x ≤ 40 mol%. The Raman, IR spectra of these samples show that glass network consists of [TeO3]/[TeO3+1], [TeO4], [WO4] and [WO6] groups as basic structural units. The W ion coordination state changes from 4 to 6 when WO3 concentration increases beyond 30 mol%. Addition of WO3 oxide to the TW glasses increases the amount of lower coordination of [TeO3]/[TeO3+1] units and decreases the higher coordination [TeO4] units, Te–O–Te chains. From DSC thermogram, thermal properties such as the glass transition temperature (Tg), onset crystallization (To) of the glass systems were calculated. The compositional variation of glass transition temperature (Tg) is found to linear with an increase in WO3 content.

A B S T R A C T Alumino-tellurite glasses with wide range of Al 2 O 3 concentration (1 to 20-mol%) are prepared and their short-range structural and thermal properties are studied by Raman spectroscopy, 27 Al Magic Angle Spinning Nuclear Magnetic Resonance (MAS-NMR) and Differential Scanning Calorimetry (DSC). Glass sample with 1-mol% of Al 2 O 3 has TeeO coordination of 3.66, which is close to the value of 3.68 reported in pure TeO 2 glass. TeeO coordination decreases steadily to 3.33 on increasing alumina content to 20-mol%. 27 Al MAS-NMR studies found that Al ions exist in hexa, penta and tetrahedral coordination in the alumino-tellurite network. On increasing alumina content from 3 to 20-mol%, the concentration of hexa-coordinated AleO units decreases from 54% to 35% with a simultaneous increase in the concentration of penta and tetra coordinated AleO units. Glass transition temperature increases with increase in Al 2 O 3 concentration and correlates directly with the average si...

The thermal characteristics of the quaternary TeO 2 –ZnO–Na 2 O–Er 2 O 3 glass system as a function of rising Er 2 O 3 mol% have been studied from the kinetic point of view. Differential scanning calorimetry technique under non-isochronal conditions at various heating rates has been used to define the characteristic temperatures of the glasses (i.e. glass transition, crystallization) in addition to the glass stability parameters. The activation energies required for both the glass transition and amorphous to crystalline transformation have been computed by different methods. The mode of the glass crystallization has been determined in terms of the Avrami kinetic constant to identify the crystallization succession. Quantitative analysis of the thermal characteristics and kinetic parameters of the glass were achieved in terms of cross-linking density, number of bonds, and the bond stretching force.

We investigated the near-infrared luminescence characteristics as a function of glass composition and Tm3+ ion concentration in a new type of Tm3+-doped tellurite glass: (1−x)TeO2–(x)PbF2. In the experiments, absorption measurements were first performed to determine the spontaneous emission probabilities and the radiative lifetimes for the 4f–4f transitions of the Tm3+ ions by using the Judd–Ofelt theory. Luminescence measurements show that