Binary Glasses Research Articles

Studies on the influence of structure units on the state of ytterbium ions in TeO2-based glasses

Abstract

Creep behaviors of Ta-alloyed Cuzr-Based metallic glass composite

In the current work, the tensile creep behaviors of a (Cu0.5Zr0.5)92Ta8 metallic glass composite were investigated. The precipitates and the metallic glass matrix in the as-spun ribbons have nearly same compositions. The addition of Ta element enhances the thermal stability of binary Cu50Zr50 metallic glass. The apparent activation energies of tensile creep increase with the applied stress, and the values of strain rate sensitivity decrease from 0.39 to 0.16 with the increasing applied temperatures. The correlationship of activation energy and activation volume suggests that the largest activation energy corresponds to the smallest activation volume, and vice versa. The values of strain rate sensitivity are noticeably smaller than reported values, which is related to the softening of (Cu0.5Zr0.5)92Ta8 ribbons with the increasing creep temperatures.

Decoupling between thermodynamics and dynamics during rejuvenation in colloidal glasses**Project supported by the MOST 973 Program (No. 2015CB856800). K. C. also acknowledges the support from the NSFC (No. 11474327, 11874395).

We rejuvenate well-aged quasi-2D binary colloidal glasses by thermal cycling, and systematically measure both the statistical responses and particle-level structural evolutions during rejuvenation. While the elastic moduli and boson peak are continuously rejuvenated with the increasing number of cycles, the mean square displacement (MSD) fluctuates significantly between the different groups of thermal cycles. The decoupling between the thermo-dynamical and dynamical evolutions suggests different microscopic origins for the different bulk properties of glasses. We find that a small fraction of structural rearrangements triggered by thermal cycling can alter the whole elastic continuum and lead to the significant thermodynamic rejuvenation, while localized defects can be activated and deactivated at the positions close to the rearrangements with significantly high mobility change and hence result in the fluctuated dynamics even with only about 10% of the particles as fast regions. Our results offer a comprehensive picture for the microscopic mechanisms underlying bulk glass rejuvenation, which can be readily used to refine glass properties or to formulate further statistical theories in glassy systems.

Thermal Stability of Type II Modifications by IR Femtosecond Laser in Silica-based Glasses.

Femtosecond (fs) laser written fiber Bragg gratings (FBGs) are excellent candidates for ultra-high temperature (>800 °C) monitoring. More specifically, Type II modifications in silicate glass fibers, characterized by the formation of self-organized birefringent nanostructures, are known to exhibit remarkable thermal stability around 1000 °C for several hours. However, to date there is no clear understanding on how both laser writing parameters and glass composition impact the overall thermal stability of these fiber-based sensors. In this context, this work investigates thermal stability of Type II modifications in various conventional glass systems (including pure silica glasses with various Cl and OH contents, GeO2-SiO2 binary glasses, TiO2- and B2O3-doped commercial glasses) and with varying laser parameters (writing speed, pulse energy). In order to monitor thermal stability, isochronal annealing experiments (Δt⁓ 30 min, ΔT⁓ 50 °C) up to 1400 °C were performed on the irradiated samples, along with quantitative retardance measurements. Among the findings to highlight, it was established that ppm levels of Cl and OH can drastically reduce thermal stability (by about 200 °C in this study). Moreover, GeO2 doping up to 17 mole% only has a limited impact on thermal stability. Finally, the relationships between glass viscosity, dopants/impurities, and thermal stability, are discussed.

Structure and Raman spectra of binary barium phosphate glass

Structure and Raman spectra of binary barium phosphate glass

Structure and Raman spectra of binary barium phosphate glasses

The structure of xBaO·(1 − x) P2O5 (x = 0.30, 0.35, 0.40, 0.45, and 0.50) glasses was studied by Raman spectroscopy and thermodynamic model Shakhmatkin and Vedishcheva (SVTDM). The seven system components (defined as stable crystalline phases of the BaO–P2O5 binary phase diagram) were considered in the SVTDM: BaO, P2O5, 4BaO·P2O5 (B4P), 3BaO·P2O5 (B3P), 2BaO·P2O5 (B2P), BaO·P2O5 (BP), and BaO·2 P2O5 (BP2). Only the equilibrium molar abundances of BP and BP2 were non-negligible in all studied glass compositions. Therefore, in the next step, multivariate curve analysis (MCR) of the baseline—subtracted, thermally—corrected experimental Raman spectra, was performed for two components (BP2 and BP). MCR resulted in the Raman spectra (loadings) and relative abundances (scores) of each considered component. The MCR method reproduced 98.93% of the spectral data variance. Then, the decomposition of Malfait was used. The perfect fit between the MCR loadings and the partial Raman spectra of BP2 and BP, obtained by Malfait’s decomposition, was found, confirming the validity of thermodynamic model.

Structure and morphology of new PbBr2-B2O3 glasses analyzed by spectroscopic techniques

Different glasses were prepared using the normal slowly cooled melting technique in the binary xPbBr2(100 − x)B2O3 (10 ≤ x ≤40 mol%) system. The methods used to analyze the microstructure of the binary PbBr2-B2O3 glasses are Nuclear Magnetic Resonance (NMR), Fourier Transform Infrared (FTIR), Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD). The structural units of the borate matrix are established from spectroscopy of 11B NMR. The main structural species which build up the borate network are the triangle BO3, boroxol-like rings and tetrahedral BBr4 groups. FTIR spectroscopic technique also supported the existence of these borate units. The PbBr2 cannot be used as an additive modifier but it produces a crystalline Pb2B5O9Br mixture that is impeded in the glass matrix. The species BO3 is the primary complement of the species Pb2B5O9Br. NMR and FTIR spectroscopy confirmed the nature of BO3 components. On the other hand, there is no evidence of BO4 species in the material being studied. NMR spectroscopy reveals a very low concentration of (BBr4) tetrahedral (boron combined with Br). In these materials, the TEM and SEM micrographs as well as EDP (electron diffraction patterns) and x-ray diffraction analyses reported the development of crystalline Pb2B5O9Br phases. The electrical resistivity is extremely high in the investigated samples, their value close to the fused B2O3 limit.

Thermal and optical properties of binary magnesium tellurite glasses and their link to the glass structure

Binary magnesium tellurite glasses x MgO, (100-x) TeO2, studied to determine their glass forming range, structure, thermal and optical properties. Glasses were successfully synthesis in the range x = 10–45 mol%. Addition of 50 mol% of MgO leads to the appearance of the Mg3TeO6 crystalline phase. The molar volume decreases linearly with increasing MgO content. Both glass transition and crystallization temperature increase with increasing MgO content. The deduced glass stabilities show a slight maximum for x = 25 and 30mol%. Studying the structure of these glasses using Raman spectroscopy reveals the transformation of trigonal bipyramid TeO4 (tbp) structural unit to the trigonal pyramid TeO3 units with the intermediate phase TeO3+1. The coordination of Te–O decreases with increasing MgO content. The UV–Vis spectra show a shift of the UV-cutoff toward higher energy and the measured refractive index decreases with increasing MgO. Optical band gap was estimated and the obtained values were used to calculate molar refractivity, molar polarizability and a calculated refractive index. The metallization criterion is found in the range (0.399–0.417) indicating good optical nonlinearity of the prepared glasses.

Deformation-Enhanced Hierarchical Multiscale Structure Heterogeneity in a Pd-Si Bulk Metallic Glass

The multiscale structures in a Pd82Si18 binary bulk metallic glass before and after bending were studied using electron microscopy, high-energy synchrotron X-ray diffraction, and small-angle X-ray scattering. The experimental results revealed the enhancement of hierarchical structure heterogeneities on multiple length scales after deformation. Hierarchical multiple shear bands of high number density can be observed after bending, introducing complex but periodically distributed residual strain. Pair distribution function analysis revealed that the connectivity of the short-range cluster on the medium-range scale determines the packing density difference between the tension side and the compression side in the sample after bending. The electron density fluctuations on the nanoscale observed in the deformed part of the sample are indicative of a nanoscale amorphous phase separation induced by plastic deformation. Our findings will deepen the understanding of the plastic deformation mechanism of metallic glasses and shed light on designing glassy alloys of excellent plasticity and toughness through hierarchical multiscale structure heterogeneities.

Applicability of different models of energy bandgap and refractive index for chalcogenide thin films

The optical parameters are critical factors for the development of optoelectronic devices. Here the authors report the study of optical parameters based on some empirical relationship for Ga doped Ge-Te-Se. These relationships are based on the specific models proposed for the calculation of binary, ternary, and quaternary chalcogenide glasses for the specific range of energy gap. The empirically calculated values of optical parameters from these models are compared with the experimental value of the chalcogenide thin films. The values of refractive index have been calculated from the optical bandgap. Some relations proposed by different authors show good agreement between the experimental and calculated values. It has been concluded that Ravindra & Gupta, Reddy & Duffy, Kumar & Singh, and Reddy provide the satisfactory results.

Thermal stability and ionic conduction characteristics of lithium germanate glasses

A report is given of the systematic investigation on the glass stability and conduction characteristics of binary lithium germanate glasses in the series, mol% xLi2O-(100-x)GeO2, 5 ≤ x ≤ 30. The glass stability (against devitrification) parameters along with density and glass transition temperature reveal an extremum around 15 mol% of Li2O, a signature of the germanate anomaly. The analysis of impedance data in conductivity and modulus formalisms reflect different aspects of the structural changes as the amount of Li2O increases. The lithium ion conductivity increases with the increase in the Li2O concentration while the activation energy for ionic motion does not change much from mol% 5 to 10 Li2O and decreases monotonically from mol% 10 to 30 Li2O indicating the absence of germanate anomaly. However, the data in modulus formalism does not scale to a master curve for all the glasses suggesting the germanate anomaly. Modeling of the modulus data using the Kohlrausch-Williams-Watts (KWW) function depicts the germanate anomaly in the stretched exponential parameter (β) at 15 mol% Li2O. Raman spectra of the glasses reveal the preferential formation of Q2 units at low alkali concentration along with the formation of ring structures of several Ge tetrahedra and/or the formation of higher coordinated Ge species around the anomalous composition region. A correlation of these structural changes with the conduction characteristics of the glasses is also discussed.

Features of electronic polarizability and approach to unique properties in tellurite glasses

AbstractTellurite glasses showing unique properties such as low phonon energy and high linear and nonlinear optical properties have been considered as promising materials for photonic device applications. The present article reviews the current status of the electronic polarizability in binary and ternary tellurite glasses and approaches their unique properties. Tellurite glasses consisting of basic modifier oxides (eg, Na2O, ZnO) and basic conditional glass forming oxide (TeO2) exhibit the features of high electronic polarizability and weak chemical bond strength, that is, refractive index‐based large oxide ion polarizability αO2‐(no), large optical basicity ∧(no), small interionic interaction parameter A(no), and small single bond strength BM‐O. The values of αO2‐(no), ∧(no), and A(no) in several tellurite glasses containing WO3, Nb2O5, and Bi2O3 were estimated in this article, and a good correlation was confirmed between ∧(no) and A(no). Unique properties of low glass transition temperature, fragile structural relaxation behavior, poor mechanical properties, high third‐order nonlinear optical susceptibilities in tellurite glasses were discussed from the point of electronic polarizability.

A new approach for dynamic mechanical thermal analysis: The energy dissipation rate method

We report for the first time a new approach for analyzing the DMTA spectra of the internal friction of binary systems (polymer – additive) - the energy dissipation rate method. The method involves representation of the loss spectrum in the free damp oscillation (FDO) mode in the form: absorption coefficient α(ν) = Λ(ν)*f(ν), where Λ(ν) is logarithmic decrement of oscillation and f(ν) is frequency of free damp oscillation (ν ≈ 0,7Т°К). The experimental data presented in these coordinates allows for: (1) correct application of all mathematical operations with the spectra α(ν), as with ordinary optical absorption spectra; (2) quantification of the individual components' contributions to the spectra of internal friction in multicomponent systems (composites, polymers with residual solvent, porous sorbents, glass forming systems and many others). The study investigated a model binary glass forming system made up of poly (vinyl-formal) - glycerol. The results of analysis of the loss spectra in FDO mode, associated with the additive (glycerol), correspond well to data received from far IR and dielectric spectroscopy of the dopant.

Vanadium structural role in binary fluoride borate glasses and effects of gamma irradiation

Three binary fluoroborate glasses from the systems LiF–B2O3, NaF–B2O3 and CaF2–B2O3 (50 mol% each) together with V2O5-doped derived samples from the same three systems were prepared. Collective optical, FTIR and ESR spectral measurements were carried out before and after gamma irradiation (6 M rad dose). FTIR spectra of the studied glasses reveal mostly repetitive vibrational curves with limited variations. The IR spectra show condensed vibrations due to both triangular (BO3) and tetrahedral coordinated fluoro-borate groups (BO3F) in their distinct and characteristic wavenumbers similar to that obtained from Li2O–B2O3, Na2O–B2O3 and CaO–B2O3 glasses. Gamma irradiation causes limited increase of the UV absorption within the optical spectra of undoped glasses and the generation of an induced small curvature in the visible. This behavior is related to some photochemical effects and the formation of (BOHC) or (NBOHC) or even similar fluoride analogues. The V2O5-doped glasses show some shielding behavior towards gamma irradiation and the spectral curves remain almost unaffected.ESR spectra show distinct signals for the undoped glass correlated with trace ferric oxide impurity. The V2O5-doped glasses before irradiation reveal three small signals indicating that the vanadium ions exist in V5+ with no unpaired electron and the few percent of low valence (V3+, V4+) ions producing the identified small signals. Gamma irradiation decreases the intensities of the small signals due to lower valence vanadium ions but causes the splitting of the main signals for the undoped and V2O5 doped samples. The calculated N4 values are correlated with both ability of V2O5 to promote more (BO4) or (BO3F) units and the variations are correlated with housing behavior of LiF and NaF as modifiers while CaF2 which can form some (CaF4) units.

Response to comment on “The fragility of alkali silicate glass melts: Part of a universal topological pattern”

In their Comment, Wilkinson and Mauro (WM) raise the issue that our coarse-graining interpretation of the fragility in network forming glasses lacks the first derivative quality inherent in their temperature-dependent constraint theory (TDCT). In response, we clarify this issue and acknowledge that both approaches are in conflict and each is struggling for validation. As something of a way forward, we challenge proponents of TDCT to resolve a puzzle in the fragility trends of simple binary alkali oxide glasses.

Emergent structural length scales in a model binary glass - The micro-second molecular dynamics time-scale regime

It is now possible to routinely perform atomistic simulations at the microsecond timescale. In the present work, we exploit this for a model binary Lennard-Jones glass to study structural relaxation at a timescale spanning up to 80 μs. It is found that at these longer time-scales, significant mobility and relaxation occurs, demonstrating a reproducible relaxation trajectory towards a class of asymptotic structural states which are strongly heterogeneous. These structures are discussed both in terms of the ideal glass state and a production route towards novel amorphous crystalline nano-composite micro-structures with strong interface stability.

Properties and structure of SnO−SiO2 and SnO−SnF2−SiO2 glasses

Binary SnO−SiO2 and ternary SnO−SnF2−SiO2 glasses are investigated as potential alternative to lead containing glasses for the development of optical components using polarization light. Optical and thermal properties (including very small photoelastic constant, PEC) are reported herein. A minimum value of PEC (–0.008 × 10−12 Pa−1) is measured at a wavelength of 632.8 nm for the binary glass containing 43.6 mol% of SnO. The ternary glasses with fluorine of 8 − 9 mol% provide a very small PEC (–0.039 × 10−12 Pa−1) and blue-shifted optical absorption edge for 47.0 mol% of SnO+SnF2. The local structure of the silicate glass is investigated by micro-Raman and 119Sn, 29Si, and 19F nuclear magnetic resonance spectroscopies. It turns out that the zero PEC glass possesses a discrete silicate structure with meta- and pyro-silicate units. The relationship between the zero photoelastic property and the silicate structure is discussed.

Probing the Degree of Heterogeneity within a Shear Band of a Model Glass.

Recent experiments provide evidence for density variations along shear bands in metallic glasses with a length scale of a few hundred nanometers. Via molecular dynamics simulations of a generic binary glass model, here we show that this is strongly correlated with variations of composition, coordination number, viscosity, and heat generation. Individual shear events along the shear band path show a mean distance of a few nanometers, comparable to recent experimental findings on medium range order. The aforementioned variations result from these localized perturbations, mediated by elasticity.

Study of Metal-Induced Effects of Cd, Sb and Zn on d.c./a.c. Conduction and Photoconduction in Binary Se70Te30 Glass

This paper reports the temperature dependence of d.c. and a.c. conductivity in the glassy alloys of Se70Te30 and Se70Te28M2 (M = Cd, Sb, Zn). The role of the Cd, Sb, Zn elements as foreign atoms has been examined on the d.c./a.c. conduction and photoconduction in binary Se70Te30 glass. These multi-component chalcogenide glasses have been prepared by conventional, cost-effective and well-known melt-quench technique. Thermally activated a.c. conduction shows the presence of the compensation effect that is confirmed by the Meyer–Neldel relation between the associated activation energy and the pre-factor of a.c. conductivity. The metal-induced effects of Cd, Sb, Zn on the photosensitivity of parent glass are also discussed.

Theoretical calculus of the mechanical strength of binary oxide glasses

The mechanical strength of the glasses is determined by the strength of the established bonds between the different macro-anionic species, these bonds being the weaker compared to the covalent ones inside the macro-anionic species. In this paper is proposed a probabilistic relationship to calculate the theoretical mechanical strength of the SiO2 glass and of some compositions in the Na2O⋅Si2 system, in good agreement with literature data.