Microstructure and crystallization properties of TeO2–PbF2 glasses (original) (raw)
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Investigation of Infrared and Raman Spectraof TeO2Nb2O5TiO2 Glasses
X-ray diraction, infrared (IR), Raman spectroscopy and scanning electron microscope techniques have beenused to investigate the microstructural properties of the glass materials. In this work, a new type of tellurite based optical glasses with TeO2/Nb2O5/TiO2 for dierent xNb2O5 (x = 5, 10, 15, and 20 mol.%) glass compositions at constant 5 mol.% TiO2 ratio were prepared. The eect of Nb2O5 contents on the structural unit of (95x)TeO2 (x)Nb2O55TiO2 glass network, and the intensity ratios of the Raman peaks were investigated. The results indicate that for dierent Nb2O5 content 5 to 20 mol.% in the glass system, three vibrational peaks around 650, 800, and 920 cm1 which correspond to the structural bonding of the glass were observed in the range of 5002000 cm1 for the IR spectra. Furthermore, from the Raman results a structural evolution was determined with the number of structural units such as [NbO6]7, TeO3+1 (polyhedra), TeO4 (trigonal bipyramids), TeO3 (trigonal pyramids) or TeO3+1 (polyhedra), and [NbO4]3 for this ternary glass system.
Thermal and structural study of glasses in the binary system TeO2–Pb(PO3)2
Journal of Non-Crystalline Solids, 2013
The main objective of this work has been to prepare and characterize the thermal and structural properties of glasses in the pseudo binary system TeO 2 -Pb(PO 3 ) 2 with respect to the composition. Homogeneous and transparent glass samples were obtained by the melt-quenching method in a large glass forming range in the pseudo binary system (100 − x)TeO 2 -xPb(PO 3 ) 2 with x varying from 5 to 100. Thermal properties investigated by DSC pointed out an increase of the glass transition temperature from x = 5 to x = 40 and further decrease of Tg for higher Pb(PO 3 ) 2 concentrations. A similar tendency has been observed for the thermal stability against devitrification measured using the stability parameter Tx-Tg. FTIR together with Raman spectroscopies allowed building a structural model for these glasses with the contribution of distinct phosphate and tellurite units depending on the composition. Identification of crystalline phases obtained after the glasses heat-treatments obtained by X-ray diffraction support the structural evolution suggested by vibrational spectroscopies. These data suggest that incorporation of TeO 2 in the lead metaphosphate glass results in tellurium conversion from TeO 4 seesaw geometry to TeO 3 trigonal pyramids and consequent conversion of well-known metaphosphate units Q 2 to modified pyrophosphate units Q 2 1Te in which the phosphorus PO 4 tetrahedron is linked to another PO 4 unit and one TeO 3 pyramid. These tellurite trigonal units cross-link the modified metaphosphate chains with a resulting increase of the glass network connectivity. For high TeO 2 concentrations, all Q 2 were converted to Q 2 1Te and the additional tellurium atoms are incorporated in the glass network as TeO 4 seesaw units with a glass network built from a tridimensional network of TeO 3 , TeO 4 and Q 2 1Te . Finally, this work pointed out the possibility to use this pseudobinary system for the preparation of phosphate glass-ceramics containing a TeO 2 crystalline phase or tellurite glass-ceramics containing a pyrophosphate or metaphosphate crystalline phase.
The (1−x)TeO2–xPbF2 binary glass system was investigated by differential thermal analysis (DTA) and ultraviolet–visible-near-infrared (UV–VIS-NIR) absorption spectrophotometer. Samples were prepared by melting the mixture of TeO2 and PbF2 in a platinum crucible at 800 ◦C in air. Glass transition and the crystallization temperatures as function of the glass composition were measured by DTA. An exothermic peak of crystallization temperature was observed at about 340±1 ◦C for all three samples. A second peak of peak crystallization temperature was observed at about 400 ◦C for only the sample with 0.15 mol PbF2. The mechanism and the activation energy for each crystallization peak were determined from the DTA curves measured with different heating rates between 5 and 20 ◦C/min. The mechanism of the crystallization was found to be surface crystallization for the first exothermic peak for only 0.15 mol PbF2 sample; on the other hand, bulk crystallization was found for all samples. Corresponding activation energies are 814, 748, and 387 kJ/mol for the samples with 0.10, 0.15 and, 0.25 mol PbF2, respectively. The mechanism and the activation energy for the second exothermic peak observed in the sample with 0.15 mol PbF2 were found to be bulk crystallization and 415 kJ/mol, respectively. The optical band gap, and Urbach energies were calculated from the absorption spectra measured between 300 and 800 nm at room temperature. The optical bandgap varies from 2.02 to 1.90 eV when the PbF2 content increases from 0.10 to 0.25 mol in the glass matrix.
Structural studies on TeO2–PbO glasses
Journal of Physics and Chemistry of Solids, 2001
Binary tellurite-based glasses in the TeO 2 ±PbO system were prepared and its structure investigated by means of Raman Scattering and X-ray Absorption Spectroscopy. Both spectroscopies indicate strong modi®cations of the ®rst coordination shell around tellurium atoms when the PbO content increases revealing for lead its glassy network modi®er role. Also, Pb L 3-edge EXAFS measurements reveal this structural role played by lead atoms, but the presence of a medium range order contribution indicates that lead also participates to the glassy network formation.
Influence of modifier oxides on the structural and optical properties of binary TeO2 glasses
Journal of Applied Physics, 2007
Five different glass compositions with equal TeO 2 molar concentration and various intermediate constituents were prepared to examine the influence of such intermediate species on the tellurite network. A correlation between the glasses' structural network and optical properties is presented. Peak Raman gain coefficients, on the order of 40 times the gain of SiO 2 , are reported in this paper.
AIP Conference Proceedings, 2017
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 (XRD), Differential Scanning Calorimetry (DSC), Raman and UV-visible spectroscopy. Titanium tellurite glasses require high melt-cooling rates and were fabricated by splat quenching. On adding B 2 O 3 , the glass forming ability (GFA) enhances, and 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 Te-O) decreases with the increase in B 2 O 3 as well as Bi 2 O 3 content while, TiO 2 produce only a small decrease in N Te-O , which explains the lower GFA of titanium tellurite glasses that do not contain Bi 2 O 3 and B 2 O 3. 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.
Raman and crystallization behaviors of TeO2–Sb2O4 glasses
Journal of Non-Crystalline Solids, 2003
Transparent glasses obtained in the TeO 2-Sb 2 O 4 system have been investigated by Raman spectroscopy and differential scanning calorimetry. The glass transition temperature evolution registered in function of the composition was correlated to the structural modification of the glass network. Temperature programmed X-ray diffraction allowed the identification of the different phases that appear during the crystallization of these glasses. A correlation between the structure of the initial crystalline phase and the local structure of the glass was discussed.
Synthesis optical properties of novel TeO2 based glasses
Optik, 2016
The glasses with composition 75 TeO2-5 WO3-15 Nb2O5-5NiO, 78 TeO2-5 WO3-15 Nb2O5-2NiO and 78 TeO2-5 WO3-15 Nb2O5-2NiCl in mol% prepared by using a conventional melt-quench technique. Thermal stability (ΔT), glass transition temperature (Tg) of prepared glasses were determined by using DTA technique. It was noticed that the glass with the composition 78 TeO2-5 WO3-15 Nb2O5-2NiCl has the highest value of Thermal stability (ΔT=119 ᵒ C) and the lowest value of glass transition temperature (Tg = 414 ᵒC). Raman spectroscopic studies showed that the glass network consists of TeO4, TeO3+1, TeO3 , WO4 , WO6 and NbO6 units as basic structural units. The ratio of TeO3/TeO4 was determined as a measurement of the non-bridging oxygen / bridging oxygen bonds in the network structure. Transmittance and absorbance were measured by a spectrophotometer in the spectral range of 190-2500 nm. Some optical properties such as the optical band gap (Eopt) , absorption coefficient(α), refractive index (n) and the cut off in UV and IR bands to the bandpass filter were calculated from the absorbance and transmittance, which confirmed the optical properties of this type of filter.
Structural and optical study of glasses in the TeO 2 -GeO 2 -PbF 2 ternary system
Journal of Non-Crystalline Solids
New glass compositions were investigated in this specific proportion (90-x)TeO 2-10GeO 2-xPbF 2 in order to study the influence of lead fluoride content on the thermal, structural and optical properties. Glass samples with x = 5 to 30% were prepared by melt-quenching method. Thermal characterizations by DSC allowed to identify a clear decrease of the glass transition temperature as well as a very distinct crystallization behavior for higher PbF 2 contents. Raman spectroscopy suggests a progressive PbF 2 incorporation with conversion of TeO 4 to TeO 3 units related with the modifier behavior of PbF 2 in the glass network. X-ray diffraction patterns of crystallized samples support these results since crystalline TeO 2 was detected for lower PbF 2 contents whereas lead tellurite Pb 2 Te 3 O 7 was identified for the most lead fluoride concentrated sample. UV-Vis-NIR absorption spectra are in agreement with a progressive increase of the optical bandgap with lead fluoride concentration. Emission spectra of Eu 3+ doped samples also pointed out a progressive structural change around Eu 3+ ions with more symmetric sites. Finally, experimental lifetimes, Judd-Ofelt parameters and quantum efficiencies were obtained from these samples and exhibited a strong dependency of the lead fluoride contents, suggesting that these new fluorotellurite glasses are interesting hosts for rare earth ions.
Influence of modifiers on thermal and optical properties of TeO2–P2O5–ZnO–PbF2 glasses
Optica Applicata, 2019
A series of fluorotellurite glasses based on 70TeO2–5MxOy–10P2O5–10ZnO–5PbF2 in mol%, where MxOy = (WO3, Nb2O5) doped with 2400 ppm of Er2O3 have been prepared by the conventional melt quenching method. The influence of modifiers on thermal and optical properties of glasses has been analyzed. Thermal characteristics of glasses like the glass transition temperature Tg, the temperature for the crystallization onset Tx, the maximum crystallization temperature Tc, and the thermal stability parameter were determined by the DSC method. The ellipsometric data have provided Sellmeier-type dispersion relations of the refractive index of the investigated glasses. The optical parameters are used to calculate the molar refractivity, molar polarizability, oxide ion polarizability, molar cation polarizability, and a number of polarizable atoms per unit volume for every glass composition in order to interpret the refractive index of these glasses.