Thermal Properties Of Glasses Research Articles

Impact of aluminum fluoride addition on crystallization, structure and thermal properties of lead borate glasses

The glass composition (70-x)PbO–(30-y)B2O3–(x+y)AlF3, where x and y ranges from 0 to 20 mol%, were prepared using the conventional melt-quenching-annealing technique. The structural and thermal properties of the glasses were comprehensively analyzed using techniques like Differential Thermal Analysis (DTA), Dilatometry, Fourier-Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). XRD confirmed the amorphous, non-crystalline structure of the glasses. The glass network was found to be composed of structural units such as PbO4, BO4, BO3 and AlO6 using FTIR spectroscopy. FTIR analysis revealed significant structural changes, including the transformation of BO4 to BO3 units and the increase in non-bridging bonds, particularly with higher AlF3 content. DTA was instrumental in determining characteristic temperatures, such as the glass transition, melting, and peak crystallization temperatures, along with glass stability parameters (∆T, Hr, Tgr) for all samples. The study found that the addition of AlF3 led to a decrease in these characteristic temperatures when replacing B2O3, but an increase when replacing PbO. Variations in the density and thermal expansion of the lead borate glass were observed upon the addition of AlF3, decreasing when substituting for PbO and increasing when substituting for B2O3. These findings provide insights into the properties of oxyfluoride glasses, paving the way for future optimization in their composition for varied applications.

XPS, FTIR, DSC and optical absorption investigations on 55B2O3–20ZnO–(25-x)Li2O–xBi2O3 (0≤x≤25 mol%) glass system

Melt quenching was employed to synthesize 55B2O3–20ZnO–(25-x)Li2O–xBi2O3 (0≤x≤25 mol%) glass system. XRD, FTIR, DSC, EDX, XPS and optical absorption studies were conducted to elucidate structural, thermal and optical properties of glasses. Both XRD and DSC patterns proved the non-crystallinity of glasses. EDX analysis disclosed the existence of all constituent ions in the respective glasses. FTIR spectra illustrated that the glass contains BO3, BO4, BiO6 alongside B-O-B and mixed covalent and ionic Zn-O-B/B-O-Bi/Zn-O-Bi/Bi-O-Bi linkages. Variations in thermal properties of glasses were corroborated with physical and structural investigations. The variations in optical properties like Eopt, ∆E, n, M, RM, Ʌth and αo2− were well correlated with structural changes occurred with Bi2O3. XPS data validated the existence of non-bridging oxygens and found to be responsible for the variations in optical properties of all glasses. The high thermal stability of BZLBi3 could be useful for fiber drawing applications.

Structure-Sensitive Properties of Melts and Thermal Properties of Glasses in the B2O3–CaO–Al2O3–PbO System

Structure-Sensitive Properties of Melts and Thermal Properties of Glasses in the B2O3–CaO–Al2O3–PbO System

Effect of TiO2 on microphase development during phase separation and crystallization in Na2O–B2O3–SiO2 glass system

AbstractThis study examines the incorporation of TiO2 into sodium borosilicate glasses and its effect on the formation of glassy and crystalline microphases. Glasses in the composition range: 7Na2O–23B2O3–(70 ‐ X)SiO2–XTiO2 (where X = 0–14.6 mol.% TiO2) which exhibit phase separation were investigated. Raman studies confirm the formation of two different TiO2 coordinations depending on the molar content of TiO2. Thermal properties of glasses are unaffected by TiO2 addition. The domain size of microphase development in TiO2‐containing glass indicates competition between phase separation and crystallization. Enrichment of titanium on the interphase between glassy microphases reduces the mass transfer and consequently limits the growth rate of glassy phases. This competes with the formation of anatase for which a nucleation‐controlled mechanism is proposed.

Physico-chemical properties and structural transformations in the synthesis of boroalumosilicate glass-crystal materials

The aim of this work is to study the areas of glass formation and metastable liquation of the pseudo-ternary system (MgO·Al2O3)-B2O3-SiO2, and study of the crystallization process of glasses of cordierite composition. The crystallization process of glasses of cordierite composition containing B2O3 by a single-stage heat treatment at 1000 oC and 1200 oC, the nature of crystallization, the thermal properties of glasses and glass crystalline materials of the system (MgO·Al2O3)-B2O3-SiO2 were studied. It revealed that during the isolation of a boron-containing solid solution, the residual glassy phase enriched with oxides of MgO and Al2O3, which lead to an increase in the thermal expansion coefficient of the glass phase. The research results provide possibility to synthesize glass-ceramics with certain thermophysical parameters by stopping further glass crystallization at the stage of formation of a certain amount and ratio of the required crystalline and glassy phases.

A thorough investigation of the Bi2O3–PbCl2–TeO2 system: Glass forming region, thermal, physical, optical, structural, mechanical and radiation shielding properties

In the present work, a series of glasses in the Bi2O3–PbCl2–TeO2 system are synthesized by conventional melt quenching technique. Glass forming region of the specially designed glass system is determined. Thermal properties of glasses – glass transition (Tg) and crystallization (Tc/Tp) temperatures and glass stability against crystallization (∆T) – are determined. Density and refractive index values are measured to interpret various physical properties of glasses. Optical and structural properties are studied through visible transmittance and Fourier transform infrared spectroscopy analysis. Mechanical properties are investigated by Vickers hardness measurements. The radiation shielding competence of glasses is evaluated in the energy range from 0.161 MeV to 2.51 MeV using Phy-X/PSD simulation program. The mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), effective atomic number (Zeff), half value layer (HVL), tenth value layer (TVL) and mean free path (MFP) are calculated. Glasses in the Bi2O3–PbCl2–TeO2 system possess superior shielding effectiveness than other commercially available radiation shielding glasses owing to higher MAC and lower HVL and MFP values.

Color tunability and white light generation through up-conversion energy transfer in Yb3+ sensitized Ho3+/Tm3+ doped tellurite glasses

In this study, tellurite glasses in the (50-x)TeO2-25WO3-25Li2O-xRE (RE: Ho3+, Tm3+, Yb3+) system were synthesized to investigate white light generation through up-conversion energy transfer. Thermal properties of glasses were studied, and optical absorption spectra were collected. Energy transfer mechanisms between RE ions and effect of RE concentrations on up-conversion emission and color tunability were investigated through photoluminescence analysis under 980 nm excitation. Additionally, effect of excitation power on up-conversion emission intensities were investigated. Colorimetric properties such as CIE color coordinates, correlated color temperature, color rendering index and color purity were calculated. The obtained colorimetric results under 2 watt pump power were comparable or better than other reported glass systems. H005T025Y2 sample was found to show the closest color coordinates (x = 0.32 and y = 0.33) to pure white light and suitable colorimetric properties indicating that studied glasses have high potentiality to be used as luminescent materials for white light generation.

Dy3+ doped tellurite glasses for solid-state lighting: An investigation through physical, thermal, structural and optical spectroscopy studies

In the present work, a series of Dy3+ ion doped tellurite glasses in the (50-x)TeO2-25WO3-25Li2O-xDy2O3 system were synthesized using conventional melt quenching technique to investigate colorimetric and radiative properties of Dy3+ ions in a new and stable host for their evaluation as solid-state lighting materials. Physical and structural properties were studied through density calculations, refractive index measurements, and Fourier-transform IR spectroscopy analysis. Thermal properties of glasses – glass transition (Tg) and crystallization (Tc/Tp) temperatures and temperature difference (ΔT) – were determined using differential scanning calorimetry. Optical absorption spectra of glasses were recorded with Vis-NIR spectrophotometer. CIE color coordinates, correlated color temperature, color rendering index and yellow to blue emission intensity ratio values were obtained through photoluminescence analysis. Radiative properties such as, radiative transition probability, stimulated emission cross-section, branching ratio and optical bandwidth gain were calculated according to Judd-Ofelt theory. The obtained optical spectroscopy results were found to be comparable or better than other reported glass systems. From the derived results, glasses with Dy3+ ion concentration lower than 0.5 mol% were found to show the closest CIE color coordinate values to pure white light and highest CCT and CRI values revealing good potentiality to be used for applications in white LEDs and solid-state lasers.

О механизме поглощения и восстановления пропускания излучения в канале мелкомасштабной самофокусировки короткого лазерного импульса в неодимовом стекле

In the study of small-scale self-focusing (SSF) of a 0.5 ns Nd-laser pulse with 3-5 GW/cm2 intensity in Nd-glass samples, in addition to the characteristic filamentary damage, spectral broadening and laser radiation scattering, a jump in absorption in glasses at the wavelengths 1.06 µm and 0.66 µm was registered also. The coefficient of the induced absorption (IA) in the samples reached 0.15 cm– 1. Restoration of the transmission in the media after the end of the laser pulse had occurred over the time of 15-35ns for phosphate and 5-10 ns for silicate glasses. The physical picture of the IA effect detected as far back as the 1980-s, however, had not been clarified. Current analysis of the experimental data has shown that the absorption jump could be caused by the rapid populating of the 4I11/2 lower laser level of Nd3+ ions in glasses due to the nonlinear processes in the SSF channel: Raman scattering and spectral broadening of the laser radiation. The rates of the 4I11/2 level depopulation and recovery of the transmission were determined by dimensions of the regions with excited Nd3+ ions arising in the glass samples at the interference of laser and scattered radiation as well as by thermal properties of glasses.

Investigating the influence of transition metal oxides on temperature dependent optical properties of PbCl2–TeO2 glasses for their evaluation as transparent large band gap semiconductors

A series of ternary glasses in the MeO–PbCl2–TeO2 (MeO = Bi2O3, MoO3, Sb2O3, WO3, ZnO) system have been synthesized by conventional melt quenching technique. Thermal properties of glasses – glass transition (Tg) and crystallization (Tc/Tp) temperatures, temperature difference (ΔT) and thermal stability (S) values – were determined using differential scanning calorimetry. The influence of transition metal oxides on refractive index, position and shift rate of absorption edge, optical band gap energy (Eopt) and Urbach energy (ΔE) was investigated and their dependence on temperature was studied. The Eopt and ΔE values of all glasses studied in this work were found to be comparable with the values corresponding to some semiconductors. The glasses under study show great potential for applications in optoelectronics.

Crystallization behavior of WO3-MoO3-TeO2 glasses

In the present study, crystallization behavior of tungsten molybdenum tellurite glasses was investigated by non-isothermal methods using differential scanning calorimetry (DSC), X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM) techniques. Thermal properties of glasses were investigated to calculate the values of glass transition temperature (Tg), crystallization temperature (Tc/Tp), temperature difference (ΔT), thermal stability (S), glass transition activation energy (Eg) and fragility parameter (m). Average cross-link density (nc¯) values were calculated for the physical investigation of the glasses. The crystallization kinetics was studied at different heating rates and the values of Avrami constant (n) and morphology index (m) were calculated from the Ozawa equation and the activation energy of crystallization (Ec) was determined using the modified Kissinger equation. The crystallized and/or transformed phases and their morphologies were determined by XRD and SEM analysis. Studied glass compositions were found to be thermally stable, resistant to crystallization and therefore suitable for opto-electronic applications.

Optical and thermal properties of glasses and glass-ceramics derived from agricultural wastes

Agricultural waste ashes are used to synthesize glasses and glass-ceramics by melt-quench technique. The as-prepared as well as heat-treated samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), dilatometer, UV/Visible and photoluminescence spectroscopy. It is observed that, the higher content (> 50wt%) of rice husk ash (RHA) prevents the formation of the glasses. The optical band gap of as-quenched samples is in wide-band gap semiconductor range, i-e. 3.49–4.17eV. The coefficient of thermal expansion (CTE) is in the range of 13–16 × 10−6/°C measured. All samples are luminescent and show the blue shift as RHA increases in initial composition. The developed materials could find applications in the field of power-generation and UV–Visible light-emitting diode (LED's).

Spectroscopic studies of ZnO borate–tellurite glass doped with Eu2O3

Optical, physical and thermal properties of glasses with composition 24B2O3−(25−x) ZnO−51TeO2, x Eu2O3, mol% (where x=0.0, 0.5, 1 and 3%) were studied. The density, crystallization temperature, oxygen packing density and glassy temperature were found to increase with the addition of Eu2O3. The molar volume, optical band gap (Eg) and refractive index values were found to decrease with increasing Eu2O3 content. The FTIR measurements indicated that the continuous increase of europium concentration helped conversion of [BO3] to [BO4] groups in the base glass ZnO TeO2–B2O3. Thermal analysis reveals that the glass transition temperature Tg, the glass thermal stability ΔT and the glass forming ability Kg increased by the addition of Eu2O3. The transmission and absorption spectra of all glasses indicated that there is a decrease in the optical band gap Eg values due to the enhancement of the number of non-bridging oxygen (NBO) atoms with the addition of Eu2O3. The studied glasses have high values of nonlinear refractive index n2 and nonlinear optical susceptibility χ(3) with a good thermal stability. Thus, such glasses have promised applications in nonlinear optical devices.

Influence of modifiers on the thermal characteristic of glasses of the TeO2–P2O5–ZnO–PbF2 system

A series of fluorotellurite glasses based on 70TeO2–5MxOy–10P2O5–10ZnO–5PbF2 in mol%, where MxOy = MgO, SrO, PbO, CdO, were prepared by the conventional melt-quenching method. The influence of modifiers on the thermal properties of glasses was analyzed. Thermal characteristics of glasses such as the transition temperature T g, the temperature for the crystallization onset T x, the maximum crystallization temperature T c, and the thermal stability parameter were determined by DSC method. Analysis of the local atomic interactions in the structure of glasses has been used to explain the course of the crystallization. The formation of crystalline phases was confirmed by X-ray diffraction analysis and SEM methods. Obtained results demonstrate that the new compositions lead to good thermal properties which make these glasses promising candidates for rare earth ions doping. Low value of the glass-forming tendency parameter K H indicates high tendency to devitrify. The kind of modifiers affects the crystallization process in fluorotellurite glasses.

Kinetic Analysis of Thermal Processes in Ag-As-S-Se System Based on DSC Measurements

Thermal properties of glasses from the system Agx(As40S30Se30)100−x for x = 0, 0.5, 1, 3, and 5 at.% were investigated by differential scanning calorimetry. The DSC curves were obtained under non-isothermal conditions which allowed determination of the glass transition temperature Tg (onset temperature), crystallization temperature Tp (corresponding to the crystallization peak maximum), melting temperature Tm, crystallization enthalpy Hc, and melting enthalpy Hm. The DSC curves obtained at the same heating rate were analyzed in order to study the variation of glass transition temperature with Ag concentration. Observed Tg shift toward higher values, with increase in the heating rate, is in agreement with the Lasocka equation. Samples with 3 at.% and 5 at.% Ag were further thermally treated at different heating rates with the aim of analyzing kinetic processes of crystallization. The Moynihan and Kissinger models were used to calculate the activation energy of glass transition and activation energy of crystallization. For the samples that showed the crystallization processes an assessment of the thermal stability was done based on different criteria.

Thermal properties of MnO2 and SiO2 containing phosphate glasses

Thermal properties of glasses from the P2O5–SiO2–K2O–MgO–CaO system modified by MnO2 addition was studied by DSC, XRD and FTIR methods. It has been found that the replacement of MgO and CaO modifiers by MnO2 in the structural network of phosphate glasses results in decrease in the glass transition temperature (T g) and thermal stability parameter (ΔT). The identified crystallization products proved to be diversified, including different type of polyphosphates and silicates. It was determined that the type of the crystallizing phosphate phases is consistent with the classification of phosphate glasses, based on the O/P ratio. During the crystallization in higher temperature ranges and with the content of MnO2 over 25 mol%, a change of crystallization products was noted, including the transition of the diopside type silicate (CaMgSi2O6) into the akermanite type silicate (Ca2MgSi2O7). Simultaneously, the nature of transitions taking place during heating of the analyzed glasses was explained on the basis of crystallochemical factors (strengths of bonds) and chemical affinity of the glass components (ΔG of formation).

Experimental Study of Viscoelastic and Thermal Properties of Glasses and Polymers near Glass Transitions

Viscosity of several inorganic glasses and amorphous polymers have been measured under pure shear deformation mode by using a sandwich method and utilizing a sensitive optical technique in the temperature range from the room temperature up to the glass transition temperatures. Prom the temperature dependence of the viscosity, activation energies controlling the viscous deformation were determined. Two different relaxations were superposed in materials containing long molecular chains, while a single relaxation was observed in materials without the chain. The thermal conductivity, thermal diffusivity, and heat capacity of glasses have been determined simultaneously during an annealing or a stabilization process of glasses below the glass transition by using a hot-wire method. Three quantities showed relaxations, and the relaxation times were about the same for three quantities. The activation energy for the process was determined from the temperature dependence of the relaxation time. The relaxation time was around 300 s at the glass transition.

Influence of fluorine on thermal properties of lead oxyfluoride glass

Oxyfluoride glasses are the basic materials for obtaining transparent glass–ceramic (TGC) which can be used in a wide range of optoelectronics devices such as: amplifiers, up-conversion, telescopes, laser sources. Oxyfluoride TGC is obtained by the control heat treatment of the parent glass due to low phonon nanocrystalline phases. The oxyfluoride glasses from the sodium–lead–silica system were the object of investigation. The influence of fluoride content on the thermal properties of glasses was analyzed. Thermal characteristics of glasses like the transition temperature T g, the temperature for the crystallization onset T x, and the maximum crystallization temperature T c, thermal stability parameter were determined by DTA/DSC method. The linear expansion coefficients of oxyfluoride glasses as a function of temperature were measured using a thermo-mechanical analyzer (TMA 7 Perkin-Elmer). The effect of crystallization on the thermal expansion coefficient and softening temperature T s was found.

Ion mobility and thermal properties of glasses in the BiF3–LiF and BiF3–LiF–ZrF4 systems

Ion mobility and the characteristic temperatures of bismuth fluoride glasses in the BiF3–LiF and BiF3–LiF–ZrF4 systems were studied by Nuclear Magnetic Resonance and Differential Scanning Calorimetry methods. Analysis of 7Li and 19F Nuclear Magnetic Resonance spectra made it possible to reveal the character of ion motion in the fluoride and lithium sublattices of the glasses under temperature variation, and to determine the types and temperature ranges in which they took place. It was found that the main types of ion motion in the glasses were the diffusion of lithium ions and the reorientation of fluorine-containing groups. The diffusion of fluorine ions was observed only in crystallized glasses.

Thermochemistry of phosphate glasses for immobilization of dangerous waste

Vitrification is currently considered to be an effective method for immobilization of radioactive waste. It is based on the enclosing of harmful elements in the structure of the glass. This work presents the results of studies on the thermal properties of glasses from P2O5–Al2O3–Na2O and P2O5–Al2O3–Fe2O3–Na2O systems for rendering nuclear waste in the form of salts such as sulfates, halides, and phosphates with high sodium content. These substances are not accepted by borosilicate glass, commonly used up to now for nuclear waste immobilization. Formation of sinters of glass-waste mixtures was selected as the method for immobilization, and the thermal chemistry of this process was studied. CaCl2 was used as the model chloride waste substance. The process of immobilization consists of its sintering with Na, Al, Fe-phosphate glasses containing more than 50 wt% P2O5 as the amorphous matrix. Thermal analysis showed that all glasses exhibit an ability for crystallization, with that the intensiveness of this process is determined by the chemical composition of these glasses. The addition of Fe2O3 to the glass intensified crystallization process. Leaching of components of sinters tests established that glass containing Fe2O3 in its composition most effectively binds waste in comparison to Al2O3 containing phosphate glass. The test results allow for the statement that the waste substance in the form of chloride salts such as CaCl2 is stable bound in the glass–crystalline sinters, which ensures its effective immobilization.