Thermal expansion of glasses in the As2Se3–AsI3 system

Thermal expansion coefficients (α) of glasses in the As₂Se₃–AsI₃ system are measured in the glass transition region and temperature dependence of the fictive temperature is calculated on the basis of relaxation model. It is found that the increase of AsI₃ content results in: an increase of α, decrease of the glass transition temperature (T_g), increase of the α change at T_g, an effect of quenching rate on α, and also changes in the structural relaxation times spectrum. The data are discussed within the framework of the assumption that the addition of AsI₃ to As₂Se₃ results in: (1) destruction of the As₂Se₃ glass network, (2) structural inhomogeneity of the glasses increase, (3) the temperature dependence of chemical–structural equilibria occurring in the liquid state increases.     

Nanophase separation and effects on properties of Ge–As–Se chalcogenide glasses

Nanophase separation in the bulk Ge–As–Se chalcogenide glasses was observed by SEM and supported by XRD and IR measurements. Effects of nanophase separation on glass transition temperature (T_g), microhardness (H_v), optical band gap (E_opt) and thermal expansion coefficient (α) were investigated in terms of glass rigidity transitions. According to the correlations between the properties and average coordination number Z, it is established that nanophase separation becomes more intensive when Z is larger than 2.64.     

Preparation and properties of chalcogenide glasses in the GeS2–Sb2S3–CdS system

In searching for new kind of photoelectric material, chalcogenide glasses in the GeS₂–Sb₂S₃–CdS system have been studied and their glass-forming region was determined. The system has a relatively large glass-forming region that is mainly situated along the GeS₂–Sb₂S₃ binary side. Thermal, optical and mechanical properties of the glasses were reported and the effects of compositional change on their properties are discussed. These novel chalcogenide glasses have relatively high glass transition temperatures (T_g ranges from 566 to 583 K), good thermal stabilities (the maximum of deference between the onset crystallization temperature, T_c, and T_g is 105 K), broad transmission region (0.57–12 μm) and large densities (d ranges from 2.99 to 3.34 g cm^?3). These glasses would be expected to be used in the field of rare earth doped fiber amplifiers and nonlinear optical devices.     

Self-diffusion in the chalcogenide glass system SeGeAs

Se, As and Ge self-diffusion were investigated in three different glasses of the chalcogenide system SeGeAs by means of the radioactive tracers ⁷⁵Se, ⁷³As and ⁷¹Ge. All D values (Se between 200 and 290°C, As between 240 and 290°C and Ge between 280 and 295°C) lay between 10^?14 and 5 × 10^?16 cm² s^?1. The diffusion profiles were analyzed using a chemical micro-etching technique. Roles of glass structure and possible diffusion mechanism are discussed.     

Refractive-index dispersion of glassy semiconductors in the pseudo-binary As2Se3–SbSI system

The bulk chalcogenide glasses in the pseudo-binary system (As₂Se₃)_100?x(SbSI)_x (with x = 20, 30, 50, 70 and 80 at.%) were prepared from high-purity elemental components by melt-quenching technique. It is a system with the variable ratio of classical amorphous compound As₂Se₃ and the molecule of antimony-sulphoiodide, SbSI, which in the monocrystal form is characterized as a ferroelectric. The refractive-index behaviour (magnitude and spectral dispersion) of investigated glasses was determined by the prism method and analyzed. To calculate and discuss the parameters of dispersion in the band gap region three different approaches were used (Cauchy, Sellmeier and Wemple–DiDomenico single-oscillator model). The comparison of the results shows good agreement between all applied models. It was found that the value of the refractive-index shows normal dispersion behaviour and increases with the increase of Sb (or SbSI) content in the investigated system, whereas the optical gap of these glasses E_g slightly decreases.     

γ-ray irradiation induced multiple effects on Ge–As–Se chalcogenide glasses

In this work, multiple effects of γ-ray irradiation on properties of bulk Ge–As–Se chalcogenide glasses were studied. Increased density (ρ), thermal expansion coefficient (α) and decreased optical band gap (E_opt) were observed after irradiation, depending on glass compositions. Glasses with stoichiometric (GeSe₂)_100?x(As₂Se₃)_x compositions showed linear correlations between As₂Se₃ proportion x and irradiation sensitivity, which is expressed by Δρ/ρ, Δα/α and ΔE_opt/E_opt. Nonstoichiometric glasses (Ge₂Se₃)_100?x(As₂Se₃)_x exhibited irregular variations. The phenomena are discussed in terms of chemical bonds transition and structural evolution under γ-ray irradiation.     

Thermal and optical properties of TeO2–ZnO–BaO glasses

We report the results of a systematic study of the thermal and optical properties of a new family of tellurite glasses, TeO₂–ZnO–BaO (TZBa), as a function of the barium oxide mole fraction and compare them with those of TeO₂–ZnO–Na₂O (TZN). The characteristic temperatures of this new glass family (glass transition, T_g, crystallization, T_x, and melting, T_m) increase significantly with BaO content and the glasses are more thermally stable (greater ΔT = T_x ? T_g) than TZN glasses. Relative to these, Raman gain coefficient of the TZBa glasses also increases by approximately 40% as well as the Raman shift from ~ 680 cm^? 1 to ~ 770 cm^? 1. The latter shift is due to the modification of the glass with the creation of non-bridging oxygen ions in the glass network. Raman spectroscopy allows us to monitor the changes in the glass network resulting from the introduction of BaO.     

Glass forming region in the GeSe2–GeTe–PbTe system and some physicochemical properties of glassy alloys

New chalcogenide glasses from the GeSe₂–GeTe–PbTe system were synthesized. The glass forming region was determined using visual, X-ray diffraction and scanning electron microscopy analyses. It is extended towards the GeSe₂ and lies partially on the GeSe₂–GeTe (0–58 mol% GeTe) and GeSe₂–PbTe (20.0–57.5 mol% PbTe) sides. No glasses were obtained in the GeTe–PbTe system. The investigated physicochemical properties vary between 4.04–6.21 g/cm³ (density, d); 97–121 kgf/mm² (microhardness, HV); ?0.187 ÷ 0.007 (compactness, C) and 14.3–17.8 GPa (elasticity modulus, E), respectively.     

Sensitivity of the photo-darkening effect in CuAsSe glasses

When CuAsSe glasses are irradiated, they exhibit higher concentrations of darkening than AsSe glasses. Since darkening depends on the composition, the darkening centers in CuAsSe glasses to be of the same kind as those in AsSe glasses, i.e. arsenic clusters. Concerning the kinetics of erasing, it was found that the activation energy and the rate constant of erasing in CuAsSe are almost equal to those in AsSe glasses, but for the kinetics of darkening, it was found that the activation energy of darkening is equal to that of AsSe but α₀, which is proportional to the number of latent darkening centers, and the darkening rate constant k₁ are about twice as high as the corresponding constants of AsSe glasses. This may be the reason for the greater darkening in CuAsSe glasses. The high value of α₀ was attributed to the generation of more AsAs bonds on the addition of Cu to the AsSe glass network. The high value of k₁ was attributed to the increase in efficiency of photo-decomposition because of the many impurity levels in the band gap and also because of the narrow optical energy gap in the CuAsSe glasses.     

Glass formation and properties of chalcogenide systems (XXII) the phase diagram of the system PbSe?GeSe2 and on the compound Pb2GeSe4

The phase diagram of the system PbSe GeSe₂ is studied by X-ray analysis and DTA. Pb₂GeSe₄ is the only compound which is formed in the system. It melts incongruently at 590 ± 4°C. The formation of Pb₂GeSe₄ as a definite compound is supported by studying the phase relations in the corresponding area of the ternary system PbSe GeSe GeSe₂.     

Electron spin resonance of Mn2+ IN As–Se and As–Te glasses

The electron spin resonance of Mn has been studied in As_xSe_100?x with 0 ? x ? 70 and As_xTe_100?x with 40 ? x ? 70. All samples, except those with x < 20 in As_xSe_100?x, exhibit six hyperfine lines centered at g = 4.3. A g = 2.0 line is observed in As–Se with largely scattered linewidth by samples, but not in As–Te unless oxygen contamination is included in the samples. The g = 4.3 line in As–Se is closely related to a formation of As₂Se₃-type layer structure and interpreted as being caused by Mn situated at the interlayer position and surrounded by four Se atoms in an arrangement of rhombic symmetry. In As–Te, a similar model by four Te atoms is valid in composition near As₂Te₃, but the surrounding Te is replaced by As as As content increases. The g = 2.0 line is concluded to come from phase-separated antiferromagnetic particles of Mn–O and MnSe. The linewidth is scattere by differences in the relative amounts of the two kinds of particles and in particle size.     

Differential thermal analysis of Ag–Ge–Se,Ge–Se charge materials in the process of their heating and Ag8GeSe6, GeSe2 compound synthesis

This is the first comprehensive study of the processes of phase transformations (PT) and chemical reactions (CR) that accompany Ge–Se and Ag–Ge–Se charge material heating in stoichiometric proportions corresponding to GeSe₂ compounds, Ag₈GeSe₆ argyrodite and elementary selenium. The investigation was carried out by means of the differential thermal analysis (DTA) method. The PT in selenium and the main types of PT and CR of the formation of GeSe₂, Ag₈GeSe₆ compounds have been identified. The characteristic heats and temperature ranges of reaction processes have been determined. Ag₈GeSe₆ and GeSe₂ compounds formation has been experimentally demonstrated due to the DTA and X-ray analysis.     

Formation and structure of crystalline inclusions in As2S3–SbSI and As2Se3–SbSI systems glass matrices

The main aim of the study presented in this paper is the investigation of the structure of (As₂S₃)_100?x(SbSI)_x and (As₂Se₃)_100?x(SbSI)_x (0 ≤ × ≤ 40) glasses by Raman spectroscopy and X-ray methods, also the nature of the crystalline inclusions which arise up in their matrix at heat treatment. We have found that in conditions of continuous heating in the interval “glassforming temperature–crystallization temperature” a crystallization with predominant mechanism of stable phase SbSI separation is taking place. The formation mechanism of crystalline inclusions of antimony sulphoiodide in glass matrix is discussed in the light of our results. It was established that all investigated glasses have a nano-heterogeneous structure.     

Micro-structural studies of GeSe2–Ga2Se3–MX (MX = CsI and PbI2) glasses using Raman spectra

Microstructure of the chalcohalide glasses: GeSe₂–Ga₂Se₃–CsI and GeSe₂–Ga₂Se₃–PbI₂ ternary system were investigated by Raman spectra, lifetime of Dy³⁺ infrared emission and glass transition temperature (T_g). The evolution of the Raman spectra shows that the fundamental structural groups of these studied glasses consist of [Ge(Ga)Se₄] tetrahedral and some complex structure units [Ge(Ga)I_xSe_4?x](x = 1–4). The x value varied when the different iodide was added in Ge–Ga–Se matrix. For GeSe₂–Ga₂Se₃–CsI glasses, the [Ge(Ga)I_xSe_4?x](x = 1–4) mixed-anion tetrahedral and [Ga₂I₇]^? units occurred. For GeSe₂–Ga₂Se₃–PbI₂ glasses, the [Ge(Ga)I₂Se₂], [Ge(Ga)I₃Se] units can be formed. The changes of Dy³⁺ infrared emission lifetime and T_g support the results. Additionally, [PbI_n] structural units will be formed in GeSe₂–Ga₂Se₃–PbI₂ glasses due to high form-ability of these units when the PbI₂ content is high.     

Thermoelectric power of AsSeTe glasses

The result of the measurement of the thermoelectric power of glasses in the As₂Se₃As₂Te₃ system are reported. The results indicate that towards the As₂Te₃ end of the composition, there is an anomalous increase in thermoelectric power, the origin of which is not clear. Polaron hopping seems to contribute to conductivity in tellurium rich glasses. Structural restrictions on polaron hopping, such as the availability of AsTeAsTe chains seems to be important in discussing transport behaviour.     

Electrical and dielectric properties of MnF2–ZnF2–NaPO3 glasses

Direct electrical conductivity and dependencies of complex electrical modulus vs. temperature and frequency have been measured on glasses from the MnF₂–ZnF₂–NaPO₃ system. These glasses are sensitive to atmospheric humidity and as a consequence, the electrical conductivity increases up to temperature of 50 °C. A hydrated layer is created by the effect of water and leads to the significant increase of the electrical conductivity in the case of 0MnF₂–20ZnF₂–80NaPO₃ glass. This behavior is governed by Arrhenius relation where the values of activation energy are increasing and values of the electrical conductivity are decreasing with the amount of MnF₂. Dielectric measurements show that a heterogeneous phase is formed in the bulk of glasses. This may be seen when plotting complex electrical modulus in the complex plane. The records made by the light microscope confirmed the occurrence of the other phase in the bulk of glasses.     

Electrical and optical properties of the AsTeIn and GeSeIn chalcogenide systems

The influence of indium on the optical and properties of As_2−xTe_3−xxIn_2x, As_20−xTe_80−xIn_2x and Ge_20−xSe_80−xIn_2x is described. In Te-containing glasses the Fermi level is shifted by 0.05 eV and in Se-containing glasses by 0.2 eV towards the valence band.     

Further Meyer–Neldel rule in thermally activated crystallization of chalcogenide glasses

This paper reports the observation of the Further Meyer–Neldel rule in thermally activated crystallization in Se_80?xTe₂₀M_x (M = Ag, Cd, In and Sb); 0 ? x ? 15 chalcogenide glasses. We have investigated Further Meyer–Neldel rule by two different approaches. In the first case, the different sets of Meyer–Neldel pre-factor K₀₀ and Meyer–Neldel energy E_MN are obtained by changing the composition (i.e., value of x) of a particular glassy system keeping the third element (i.e., value of M) constant. In the second case, the different sets of Meyer–Neldel pre-factor K₀₀ and Meyer–Neldel rule energy E_MN are obtained by changing the third element in a particular glassy system keeping the composition constant. The results are explained using the conception of thermal phonons in thermally activated crystallization analogous to optical phonons in thermally activated electric conduction.     

Composition analysis of glasses in the PbBr2–PbCl2–PbF2–PbO–P2O5 system

Composition change during the melting process of some glasses in the PbBr₂–PbCl₂–PbF₂–PbO–P₂O₅ system melted at 450–470°C for 15 min was studied. Results show that there was a remarkable difference between the batch composition and the analyzed composition. Large amount of P, Br, Pb, and Cl were lost mainly in the form of PbBr₂, PbCl₂ and P₂O₅. The content of O is influenced by two factors. The incomplete decomposition of NH₄H₂PO₄ or the reaction between P₂O₅ and H₂O in the atmosphere increases the content of O, while the volatilization of P₂O₅ decreases the content of O.     

Ion conductive chalcohalide glasses in LiI–Ga2S3–GeS2 system

The electric properties of LiI containing chalcohalide glasses in the system Ga₂S₃–GeS₂ were studied by means of impedance spectroscopy and potentiostatic chronoamperometry. Two sets of the samples were prepared by direct synthesis from elements and compounds in evacuated quartz ampoules. The prepared glasses were as follows: xLiI–xGa₂S₃–(100?2x)GeS₂, x = 15, 20, 25 and 20LiI–xGa₂S₃–(80?x)GeS₂, x = 0, 5, 10, 15 and 20. In the first set the concentration of LiI increased and the second set was prepared to study the influence of Ga₂S₃ on the properties of the glasses. Additional aim of this work was to compare the electric properties of LiI containing Ga₂S₃–GeS₂ glasses with analogous AgI containing Ga₂S₃–GeS₂ glasses recently studied by us. The conductivity of the LiI containing glasses in the Ga₂S₃–GeS₂ system was higher and the activation energy was lower than in the analogous AgI containing system. The residual electronic (hole) conductivity remained similar in both systems being almost negligibly low. Raman spectroscopy proved the influence of LiI as well as Ga₂S₃ on glass structure, however interpretation of Raman spectra of these glasses is complicated due to small mass difference between gallium and germanium.