Radiation-stimulated changes in the transmission of chalcogenide glasses of As2S3−Ge2S3

The radiative-optical properties of chalcogenide glass-like semiconductors of the As₂S₂−Ge₂S₃ system in the region of a topological 2D-3D-phase transition are investigated. It is shown that γ-irradiation of samples by an absorbed dose of 4.4 · 10⁶ Gy leads to a longwave shift of their optical-transmission edge in the spectrum. The effect observed depends on the structural type of the glasses investigated and changes considerably near the 2D-3D-phase transition. Two components of the transmission-edge shift are detected: a static component, which remains unchanged for a long time after irradiation of the samples, and a dynamic one, which gradually fades in 2–3 months. It is suggested that the microstructural mechanism of these changes is attributable to processes of coordination defect formation in the structural skeleton of the samples. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, pp. 657–660, September–October, 1999.     

Electrical properties of MWCNT-composite (Se80Te20)100−xAgx (0 ≤ x ≤ 4) chalcogenide glasses

This article describes the preparation of multi-walled carbon nanotube (MWCNT) chalcogenide glass composite by the melt-quenching technique. MWCNT composite (Se₈₀Te₂₀)_100?xAg_x (0 ≤ x ≤ 4) bulk samples are characterized by the XRD, SEM and EDX. The electrical measurements were carried out in the temperature range of the 308-388 K. Cole–Cole plot has been used to determine the electrical conductivity at room temperature. It has been observed that MWCNT chalcogenide composite have higher value of electrical conductivity than pure glass. The results have been discussed on the basis of increased ionic conductivity (Ag⁺ ions) in MWCNT doped (Se₈₀Te₂₀)_100?xAg_x (0 ≤ x ≤ 4) bulk samples.     

Electrical and thermal properties of chalcogenide glass system Se75Ge25−x Sb x

The dc and thermal conductivities of five different compositions of the chalcogenide glass system Se₇₅Ge_25–x Sb _x have been studied in a temperature range below T _g. The dc conductivity results indicate that each composition has a single activation energy in the considered temperature range. The coefficient of thermal conductivity increased linearly with temperature below T _g for the compositions investigated. The increase of Sb content in the chalcogenide glass system leads to an increased coefficient of electrical conductivity , an increased coefficient of thermal conductivity , and to a decreased activation energy E and pre-exponential factor ₀. The observed compositional dependencies of and E have been correlated with the increase of weak bond density and the decrease of covalent bond density in the structure of the compositions investigated with increasing Sb content at the expense of Ge content. The decrease in ₀ and the increase in has been, respectively, correlated with the decrease in mobility and the increase in phonon velocity.     

Effect of Bi additive on structure and optical properties of amorphous BixIn25−xSe75 chalcogenide films

We report the structure and optical properties of thermally evaporated Bi_xIn_25?xSe₇₅ (0 ≤ x ≤ 7) films by using X-ray diffraction and optical spectroscopic techniques. The as-prepared samples were found to be amorphous by X-ray diffraction while the crystallization of Se, In₂Se₃ and Bi₂Se₃ phases has been observed upon annealing the films at 440 K. The enhancement in the main diffraction peak intensity was accepted as the increase in the crystalline character for the devitrified films with Bi content. The addition of 5 at.% of Bi results in the large change in the electrical parameters due to the carrier type reversal in the as-prepared samples. The red shift in the absorption edge along with a decrease in the transmittance has been observed for the as-prepared samples. The inverse relationship between optical gap and the tailing parameter (except x = 1) were observed with the increase in Bi content. The optical gap was found to increase up to x ≤ 1 and thereafter, resulted in the decrease in it for the thermally annealed samples. These results have been discussed in conjunction with the structural relaxation and impurity mediated heterogeneous crystallization of the film network.     

On the variation of activation energy for amorphous–crystallization phase transition in Se–Te–Sn chalcogenide glasses using iso-conversional analysis

In this paper, the variation of activation energy of amorphous–crystallization phase transition of as-Se_85–xTe₁₅Sn_x (x = 2, 4 and 6) chalcogenide glasses is investigated using iso-conversional analysis under non-isothermal conditions using differential scanning calorimetric (DSC) technique. The study is based on the variation of activation energy of crystallization with the degree of conversion and hence with temperature. The three iso-conversional methods of Kissinger–Akahira–Sunose (KAS), Ozawa–Flynn–Wall (OFW) and Friedman are used to deduce the variation of activation energy with the extent of conversion and also with temperature. The KAS and OFW methods give the similar values while the Friedman method gives lower values of activation energy of crystallization for the investigated chalcogenide glasses.     

Freely adjusted properties in Ge–S based chalcogenide glasses with iodine incorporation

In this study, we examined the function of halogen iodine acting as a glass network modifier in green chalcogenide glasses based on the Ge–S system. We obtained a series of Ge–S–I glasses and determined their glass-forming region. We then recorded the physical, thermal, and optical properties and studied the effect of halogen iodine on Ge–S–I glasses. Results show that these glasses have relatively wide optical transmission window for infrared (IR) applications. The softening temperature of Ge–S–I glasses varies from 210.54 °C to 321.63 °C, this temperature fits well with some kinds of high-temperature polymers, such as PES and PEI, the polymers serve as protective layers with high strength and flexibility, thus simplifying the fabrication processes of IR chalcogenide glass fiber. Finally, we performed a purification process to eliminate impurities and to improve optical spectra.     

Effect of chemical ordering on the crystallization behavior of Se90Te10−xSnx (x=2, 4, 6, and 8) chalcogenide glasses

Ternary Se₉₀Te_10−xSn_x (x=2, 4, 6, and 8) chalcogenide glassy alloys have been prepared by melt quenching technique. Various crystallization parameters, such as onset (T_c) and peak (T_p) crystallization temperatures, activation energy of crystallization (E_c) and Avrami exponent (n) have been determined for these alloys. T_c and T_p have been determined directly from the non-isothermal differential scanning calorimeter (DSC) thermograms. The value of E_c has been calculated from the variation of both T_c and T_p with the heating rate (β) according to Kissinger, Takhor, Augis–Bennett and Ozawa models while Augis–Bennett method has been used to deduce the value of n for the studied samples. The obtained values of the crystallization parameters have been correlated with the character and the energy of the chemical bonds through the calculation of the heteronuclear bond energies of the constituent atoms using Pauling principle. In addition to that, Tichy–Ticha model was used to estimate the mean bond energy of the average cross-linking per atom 〈E_cl〉, the average bond energy per atom of the remaining matrix 〈E_rm〉, and the overall mean bond energy 〈E〉 of the studied glasses. Results reveal that both of T_c and T_p decreases with increases Sn content. This is may be attributed to the decreasing in the overall mean bond energy 〈E〉. Besides, the plot of E_c (and also T_g) against 〈E〉 was found to be non linear, which contradicts the well known linear correlation between E_c and T_g with 〈E〉 as suggested by Tichy–Ticha model. This discrepancy may be due to the fact that the Tichy–Ticha linear correlation model was based on the assumption of covalent glassy network, while in the present glassy alloys, Se–Te binary doped with heavy elements such as Sn exhibit iono-covalent bonding. The calculated values of the ionicity are in support of this argument.     

Influence of the selenium content on thermo-mechanical and optical properties of Ge–Ga–Sb–S chalcogenide glasses

A number of Ge₁₇Ga₄Sb₁₀S_69−xSe_x (x = 0, 15, 30, 45, 60, and 69) chalcogenide glasses have been synthesized by a melt-quenching method to investigate the effect of the Se content on thermo-mechanical and optical properties of these glasses. While it was found that the glass transition temperature (T_g) decreases from 261 to 174 °C with increasing Se contents, crystallization temperature (T_c) peak only be observed in glasses with Se content of x = 45. It was evident from the measurements of structural and physical properties that changes of the glass network bring an apparent impact on the glass properties. Also, the substitution of Se for S in Ge–Ga–Sb glasses can significantly improve the thermal stability against crystallization and broaden the infrared transmission region.     

Surface topographic study of chalcogenide thin films of GexSb(As)40−xS50Te10 glasses

The surface topography and fractal properties of Ge_xSb(As)_40−xS₅₀Te₁₀ (x = 10, 20, 27 at.%) films, evaporated onto glass substrates, have been studied by atomic force microscopic imaging at different scales. The surface of the chalcogenide films is smooth (<5 nm roughness), isotropic and having some particular differences in texture. All films are self-similar with Mean Fractal Dimension in the range of 2.25–2.63. The films with Ge_xSb_40−xS₅₀Te₁₀ composition are more uniform in terms of surface morphology (grains structure) than those with Ge_xAs_40−xS₅₀Te₁₀ composition for which the film surface exhibits a superimposed structure of large particles at x = 10 and 20 at.%.     

Influence of plastic deformation on the magnetic properties of the Ni75Al25−cMnc solid solution

Magnetization measurements on the Ni₇₅Al_25−cMn_c solid solution (c = 0, 5, 9, 15 at%) were made as a function of temperature, magnetizing field and the degree of plastic deformation. A remarkable reduction of the spontaneous magnetization and the Curie temperature over the entire concentration was observed. A qualitative explanation on the result of Ni₇₅Al₂₀Mn₅ is given which considers the atomic configuration change, as well as a brief discussion on the results of the alloys with other Mn concentration.     

Comparison between the magnetic susceptibilities of Pd1−xAgx and single phase PdHn

The rapid decrease of the isothermal magnetic susceptibility χ of single phase PdH_n with n ( = atomic ratio H/Pd) above the critical temperature T_c = 564 differs from that of the magnetically similar single phase system Pd_1−xAg_x (x: silver mole fraction) at the same temperature and at equal valence electron concentrations (n = x), i.e. χ (PdH_n)−χ(Pd_1−xAg_x) <0. By use of a semiphenomenological susceptibility ansatz related to the nonideal solution behaviour of H (Ag) in Pd the susceptibility difference is interpreted as an electronic excess effect.The analysis of the steep descent of the magnetic susceptibility also applies to the Pd-rich side of PdH_n in the subcritical temperature region (so-called α-phase) and can be supported by ¹⁰⁵Pd Knight shift data at 348 K.     

Correlation between Meyer–Neldel rule and phase separation in Se98−xZn2Inx chalcogenide glasses

The present work reports the observation of Meyer–Neldel rule for the thermally activated crystallization of glassy Se_98−xZn₂In_x (0 ⩽ x ⩽ 10) alloys. We have observed a strong co-relation between the pre-exponential factor K₀ of rate constant K(T) of crystallization and activation energy of crystallization E_c in the present case. This indicates the presence of compensation effect for the non-isothermal crystallization process in the present glassy system, which is explained in terms of phase separation of the present alloys due to flaw bonds of these amorphous solids.     

IR impurity absorption in Sb2S3–GeS2(Ge2S3) chalcogenide glasses

The IR optical transmission spectra in the 4000–1000 cm⁻¹ (2.5–10 μm) region in the chalcogenide glasses (ChG) of the ternary Ge–Sb–S system of stoichiometric Sb₂S₃–GeS₂ and non-stoichiometric Sb₂S₃–Ge₂S₃ compositions are studied. The compositional dependences of the measured IR spectra connected with influence of O-, H- and C-based absorbed impurites are analyzed.     

The effect of Bi content on the thermal stability and crystallization of Se–Te chalcogenide glass

Glass formation and devitrification of intermediate alloys in the Se–Te–Bi system were studied by differential scanning calorimetry. A comparison of various simple quantitative methods to assess the level of stability of the glassy materials in the above-mentioned system is presented. All of these methods are based on characteristic temperatures, such as the glass transition temperature, T _g, the onset temperature of crystallization, T _in, the temperature corresponding to the maximum crystallization rate, T _p, or the melting temperature, T _m. In this work, a kinetic parameter, K _r(T), is added to the stability criteria. The thermal stability of several compositions of Se–Te–Bi was evaluated experimentally and correlated with the activation energies of crystallization by this kinetic criterion and compared with those evaluated by other criteria. All the results confirm that the thermal stability decreases with increasing Bi content in this glassy system. The crystallization results are analysed and the activation energy and mechanism of crystallization characterized.     

Mössbauer studies of the charge transfer process in the system (Li0.5Fe0.5)1−xFexFe2O4

Conclusion The formation of heterovalent pairs seems to be proved for the compounds rich in Fe²⁺ ions (x0.5) and the electron-phonon coupling seems to change with decreasing concentration of Fe²⁺ ions.Nevertheless the pairs model is not necessarily an unique interpretation of the data for x0.5 /1/ and the broadening of the Fe^m+ ions spectrum could be worked considering electronic and atomic disorders.     

Effect of replacement of Se by S on structural and physical properties of Ge–Sb–As–Se–S chalcogenide glasses

In the present study, the structural and opto-mechanical properties of Ge–Sb–As–Se–S chalcogenide glasses have been investigated. For this purpose, different bulk glasses of Ge₂₀Sb₅As₁₅Se_60?xS_x (0 ≤ x≤50) were prepared by conventional melt quenching technique in quartz ampoule and different characteristics of prepared glasses such as glass transition temperature, density, hardness, transmittance, optical band gap energy and refractive index were determined. The value of hardness and glass transition temperature of prepared glasses were found to increase with increasing the sulfur content as a result of formation of GeS₄ tetrahedral units and increasing the network connectivity and average bonding energy. The optical energy gap (according to Tauc’s relation), transmittance and refractive index of prepared glasses are in direct relation with sulfur content. In this study, the highest value of transmittance (about 70%) and lowest value of refractive index (2–2.3) was achieved in Ge₂₀Sb₅As₁₅Se₄₀S₂₀ and Ge₂₀Sb₅As₁₅Se₁₀S₅₀ glasses, respectively.     

Effect of weak neutral currents in the process e− + p → e− + γ + X

Polarization effects in the inclusive process e^– + p e^– + + X due to the neutral current are studied in the framework of the Weinberg-Salam model. Expressions for the asymmetry parameters and the degree of circular polarization of the photons are obtained in the quark-parton picture. It is shown that measurement of such quantities gives additional information about the quark structure of the hadronic weak neutral current.Paper presented at the scientific session of the nuclear physics branch, USSR Academy of Sciences and the Moscow State University on Electromagnetic and Weak Interactions (Moscow, January 16–20, 1979).Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 1, pp. 96–99, January, 1981.