Mean Bond Energy Research Articles

Stability and Percolation Threshold of Ge42–xPbxSe58 (9≤×≤20) Glasses

ABSTRACTGe42–xPbxSe58 (9≤×≤20) glassy alloys have been prepared using melt quenching technique. The samples were then subjected to differential scanning calorimetry (DSC) for recording the phase transformation occurring in the samples as a function of temperature. The characteristic temperatures of transformation, i.e. glass transition temperature, Tg, and crystallization temperature, Tc, were extracted from the DSC scans. The values of Tg and Tc were further used to ascertain thermal stability of the prepared glassy samples using Dietzel (ΔT) stability parameter. The variations of Tg with average coordination number, <CN>, were specified. It was found that ΔT exhibited a maximum at <CN>=2.44, close to the critical coordination number <CN>=2.40 optimized for maximum stability of glassy matrix. Thus, the obtained result follows Phillips-Thorpe constraint theory where the maximum stability of the network is just obtained if the percolation threshold limit is reached. The overall mean bond energies of the glassy samples were also calculated using the covalent bond approach. Glass transition temperature, Tg, was then deduced with a suitable proportionality with the mean bond energy and was compared with the experimental values.

Structure and Optical Properties of Polycrystalline InxSb30 – xSe70 (0 ≤ x ≤ 25) Chalcogenide Alloys

The spectroscopic studies of various physical properties of glassy and polycrystalline chalcogenide alloys are important due to their importance as active materials in various solid state devices. The composition dependence of these properties are explained on the basis of coordination number, but the splitting of this effect from the nature of additive is imperative for furthering the understanding of these systems. In the present work, the structural and spectroscopic investigations of melt quenched bulk In-Sb-Se chalcogenide alloys have been studied by XRD, RAMAN and optical spectroscopic techniques. The XRD study reveals the polycrystalline nature of the samples. The composition was analysed using the energy dispersive X-ray spectroscopy technique. The XRD study reveals the crystallization of Sb2Se3 and -In2Se3 phases while the increase in the intensity for -In2Se3 phase has been observed with the increase in indium content. The RAMAN spectra also reveal the formation of chalcogenide based Sb and In structural units. The diffused reflectance spectrum was used to calculate the optical absorption in 800-1500 nm spectral region and used to study the composition dependence of the optical gap in these samples. The results have been discussed in conjunction with the heterogeneous phases; density of defect states; electronegativity and average mean bond energy for these polycrystalline alloys.

Estimation of some physical characteristics of chalcogenide bulk Cd50S50 − xSex glassy systems

This work reports the determination of many of the physical properties of ternary chalcogenide bulk Cd50S50−xSex (30≤x≤50) glasses as well as the study of their dependence upon the Se-content. Mechanical milling technique was used to get a solid-state solution from elemental powders of Cd, S and Se. The phase formation of Cd–S–Se mixture was obtained by using a high energy ball milling for 48h. The product of the milling process was pressed as pellets using a compressor of pressure about 6.5MPa. The amorphous nature of bulk pellet samples has been checked using X-ray diffraction. It was found that, the values of mass density, molar volume, excess volume, field strength, compactness and the atomic density were increased, whereas the values of polaron radius and the average spacing of Se–Se, average heat of atomization, average single bond energy, mean bond energy, cohesive energy and glass transition temperature were decreased with increasing the Se concentration percent in CdSSe matrix. Heat of atomization was correlated to cohesive energy of the present Cd50S50−xSex glasses. Chemical bond approach model was used to analyze the heat of atomization, the mean bond energy and the glass transition temperature values.

Thermo-physical properties of multi-component Se78−xTe20Sn2Pbx chalcogenide glasses

Simultaneous measurements of thermal transport properties (effective thermal conductivity λe, diffusivity χe and specific heat per unit volume ρCp) of multi-component chalcogenide glasses of Se78−xTe20Sn2Pbx (0 ≤ x ≤ 6) system have been carried out at room temperature. The advanced Transient Plane Source (TPS) technique has been used for this purpose and the TPS measurements have been done on specimens in form of identical twin pellets. The various physical parameters like density ρ, molar volume Vm, compactness δ, molar mass, Mm, average coordination number, number of lone pair of electrons (LP), constraints, cohesive energy (CE), mean bond energy have been also calculated for present glasses. The results are discussed as a function of glass composition. The composition dependence of the thermal transport properties of aforesaid glassy system has also been discussed. We have observed a good agreement between the measured transport properties as a function of Pb content and those predicted by the proposed empirical exponential relation.

Structure and thermal analysis of Se100 − x(SbSn)x chalcogenide glasses

Se100−x(Sb0.5Sn0.5)x (3≤x≤12at.%) glassy alloys were prepared using the melt quenching technique. The amorphous nature of the as-prepared samples was confirmed by scanning electron microscope (SEM) and X-ray diffraction (XRD) and the effect of the addition of Sb0.5Sn0.5 content on the glass transition and crystallization kinetics of amorphous Se has been studied. The glass transition temperature (Tg) was increased with increasing content of Sb0.5Sn0.5. This behaviour was discussed in terms of glass density (ρ), cohesive energy (CE) and the overall mean bond energy <E>. The values of the activation energy of crystallization were increased with increasing Sb0.5Sn0.5 content that was confirmed by increasing the Hruby's parameter (Krg) with the increase of Sb0.5Sn0.5 content. Furthermore, the difference between Tc and Tg was increased due to the delay in nucleation process. This leads to the enhancement of the thermal stability and consequently the glass forming ability.

Effect of Compositional Dependence on the Physical Properties of Sn-Se-Sb Chalcogenide Glasses

Sn13Se87-xSbx (x = 0, 3, 6, 9, 12) glassy system is synthesized by melt quench technique. This glassy system has been studied for various physical parameters viz. coordination number, lone pair of electrons, number of constraints, bond energy, heat of atomization, glass transition temperature, cohesive energy, band gap and mean bond energy. From the physical analysis it is generalized that the average number of constraints, average heat of atomization, mean bond energy, glass transition temperature and cohesive energy are found to increase whereas numbers of lone pair of electrons calculated are found to decrease with the increase in the antimony content in the composition of the alloy. The increase in glass transition temperature has been explicated on the basis of accumulation of antimony atoms in selenium chain.

Relativistic effects for the reaction Sg + 6 CO → Sg(CO)6: Prediction of the mean bond energy, atomization energy, and existence of the first organometallic transactinide superheavy hexacarbonyl Sg(CO)6.

Our ab initio all-electron fully relativistic Dirac-Fock (DF) and nonrelativistic (NR) Hartree-Fock calculations predict the DF relativistic and NR energies for the reaction: Sg + 6 CO → Sg(CO)6 as -7.39 and -6.96 eV, respectively, i.e., our calculated ground state total DF relativistic and NR energies for the reaction product Sg(CO)6 are lower by 7.39 and 6.96 eV than the total DF and NR ground state energies of the reactants, viz., one Sg atom plus six CO molecules, respectively. Our calculated DF relativistic and NR atomization energies (Ae) are 65.23 and 64.82 eV, respectively, and so the contribution of relativistic effects to the Ae of ∼0.40 eV is marginal. The Sg-C and C-O optimized bond distances for the octahedral geometry as calculated in our DF (NR) calculations are 2.151 (2.318 Å) and 1.119 (1.114 Å), respectively. The BSSE correction calculated using the DIRAC code ∼14 kcal/mol. The relativistic DF and NR mean energies predicted by us are 118.8 and 111.9 kJ/mol, respectively, and the contribution of ∼7 kJ/mol due to relativistic effects to the mean energy of Sg(CO)6 is negligible. Ours are the first calculations of the relativistic effects for the atomization energy, mean bond energy, and energy of the reaction for possible formation of Sg(CO)6, and both our relativistic DF and the NR treatments clearly predict for the first time the existence of hexacarbonyl of the transactinide superheavy element seaborgium Sg. In conclusion, relativistic effects are not significant for Sg(CO)6.

Theoretical prediction of physical parameters of GexSb20−x Te80 (x = 11, 13, 15, 17, 19) bulk glassy alloys

Abstract Physical properties of GexSb20−x Te80 (x = 11, 13, 15, 17, 19) bulk glassy alloys are examined theoretically. Lone pair electrons are calculated using an average coordination number (〈r〉) and the number of valence electrons, and are found to decrease with an addition of Ge. Mean bond energy (〈E〉) is proportional to glass transition temperature (Tg) and shows maxima near the chemical threshold. Cohesive energy of the system is calculated using chemical bond approach. A linear relation is found between cohesive energy, band gap (calculated theoretically and confirmed experimentally) and average heat of atomization. All these parameters are increasing with an increase in Ge content. A relation between average single bond energy and photon energy is discussed. Compactness of the structure is measured from the calculated density of the glass. An attempt is made to discuss the results in terms of structure of the glass or equivalently with average coordination number.

Characterization of new quaternary Ge20Se60Sb20 − xAgx (0 ≤ x ≤ 20 at.%) glasses

The present paper reports the effect of replacement of antimony by silver on the physical parameters of new quaternary Ge20Se60Sb20−xAgx (where x=0, 5, 10, 15 and 20at.%) glasses. The average coordination number and the glass transition temperature decrease while the density, the compactness, the average heat of atomization, the cohesive energy and the overall mean bond energy increase with increasing Ag content. The overall mean bond energy increases from 59.20 to 60.99kcal/mol with an increase of the Ag content from 0 to 20at.%. The increasing cohesive energy with an increase of the Ag content has been interpreted according to the chemical bond approach. The observed dependence of the physical parameters on composition for the Ge20Se60Sb20−xAgx (where x=0, 5, 10, 15 and 20at.%) glasses can be explained on the basis of a chemically ordered network arrangement.

Dispersion and optical properties of thermally deposited Se91 − xTe9Px (x = 0, 10) films

Se91Te9 and Se81Te9P10 bulk glasses have been prepared by melt-quench technique. The amorphous nature of the as-prepared alloys is confirmed by using X-ray diffraction patterns. Thin films of Se91Te9 and Se81Te9P10 are prepared on chemically cleaned glass substrates by thermal evaporation under vacuum. Differential scanning calorimetery revealed a higher glass transition temperature for Se91Te9 in comparison to Se81Te9P10 bulk glasses. Transmission spectra of the as-prepared films are measured at normal incidence in the wavelength range of 300–2500nm. Refractive index and the film thickness were determined from optical transmittance data using Swanepoel envelope method. It was found that the refractive index dispersion data obeys the single oscillator Wemple and DiDomenico model from which the dispersion parameters were determined. The single oscillator energy, the dispersion energy, the high frequency dielectric constant and the ratio of free charge carrier concentration to the effective mass are then estimated as a function of alloy composition. Analysis of the spectral behavior of the absorption coefficient revealed an allowed indirect optical band gap in this alloy system. With phosphorus incorporation, the optical band gap is found to decrease along with a subsequent increase in the refractive index. The ensemble of these results is interpreted in terms of the chemical bond approach, electronegativity difference of the atoms, cohesive energy and overall mean bond energy.

Glass forming ability of vitreous Ge‐Te‐In system

Chalcogenide glasses from (GeTe4)100−xInx and (GeTe5)100−xInx with x = 0, 5, 10, 15 and 20 at % systems were investigated to define the glass forming ability. Parameters considered are number of constraints per atom, average coordination number and mean bond energy. The compositional dependence of these parameters is discussed in correlation with experimental obtained density, compactness and molar volume of the glasses. The stability of the glasses is confirmed through thermal properties study. Copyright © 2014 John Wiley &amp; Sons, Ltd.

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

Ternary Se90Te10−xSnx (x=2, 4, 6, and 8) chalcogenide glassy alloys have been prepared by melt quenching technique. Various crystallization parameters, such as onset (Tc) and peak (Tp) crystallization temperatures, activation energy of crystallization (Ec) and Avrami exponent (n) have been determined for these alloys. Tc and Tp have been determined directly from the non-isothermal differential scanning calorimeter (DSC) thermograms. The value of Ec has been calculated from the variation of both Tc and Tp 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 〈Ecl〉, the average bond energy per atom of the remaining matrix 〈Erm〉, and the overall mean bond energy 〈E〉 of the studied glasses. Results reveal that both of Tc and Tp decreases with increases Sn content. This is may be attributed to the decreasing in the overall mean bond energy 〈E〉. Besides, the plot of Ec (and also Tg) against 〈E〉 was found to be non linear, which contradicts the well known linear correlation between Ec and Tg 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.

Covalent bond connectivity, medium range order and physical properties of GexIn8Se92−x glasses

The GexIn8Se92−x glasses (14 ≤ x ≤ 23.5) were extensively characterized by X-ray diffraction (XRD). The chemical composition is determined using energy dispersive spectrometers (EDS). The atomic structure of these glasses is investigated by using (XRD) technique. The first sharp diffraction peak (FSDP) in the structural factor indicates the existence of medium range order (MRO) in these glasses. The position of the FSDP and its full width at half maximum (FWHM), obtained after fitting the XRD of the glasses. The repetitive characteristic distance, R and structural correlation length, L, which characterizing the intermediate structure are deduced. The effect of composition and average coordination number <CN>, on the atomic volume, the density and compactness are studied. The connectivity of the system is discussed in terms of the total number of constraints which also influence the mean bond energy of the system. The intensity of the FSDP, the atomic volume and compactness of the structure, have anomalous change at <CN> = 2.67 indicating, a topological threshold occurs. The occurrence of this dependence leads to the Ge content has a marked effect on the MRO and physical properties parameters.

A comparative study of the bonding energy in adhesive wafer bonding

Adhesion energies are determined for three different polymers currently used in adhesive wafer bonding of silicon wafers. The adhesion energies of the polymer off-stoichiometry thiol-ene-epoxy OSTE+ and the nano-imprint resist mr-I 9150XP are determined. The results are compared to the adhesion energies of wafers bonded with benzocyclobutene, both with and without adhesion promoter. The adhesion energies of the bonds are studied by blister tests, consisting of delaminating silicon lids bonded to silicon dies with etched circular cavities, using compressed nitrogen gas. The critical pressure needed for delamination is converted into an estimate of the bond adhesion energy. The fabrication of test dies and the evaluation method are described in detail. The mean bond energies of OSTE+ were determined to be 2.1 and 20 J m−2 depending on the choice of the epoxy used. A mean bond energy of 1.5 J m−2 was measured for mr-I 9150XP.

The effect of indium additive on the structural relaxation of Se–Sb–Sn semiconducting glasses

Differential scanning calorimetry (DSC) has been used to study the kinetics of structural relaxation in the glass transition region of Se80Sb12Sn8−yIny (y=0, 0.5, and 1) chalcogenide glasses, which were previously annealed at 394K below the glass transition temperature. Based on the Kovacs–Aklonis–Hutchinson–Ramos model, the dependence of the endothermic peak temperature (Tp) on heating rate has been used to evaluate the relaxation parameter. From the knowledge of this parameter the structural relaxation activation energy (Δh) has been obtained. The shift in Tp with heating rate and annealing time (ta) has been used to calculate the structural parameter, which controls the contribution of temperature and structure to the relaxation time. Results reveal that Δh decreases with In content due to the replacement of some SnSe4/2 structural units of strong bond energy by Se3In2 of weak bond energy. This reduces the cross-linking energy as well as the overall mean bond energy of the studied glasses as predicted by the chemical bond approach. The values of Δh were used to estimate the fragility index which is found to be in the range 29.7–31.7 indicating that the glasses under investigation were obtained from strong glass-forming liquids. The excess enthalpy (δH) has also been calculated, for different annealing times ta, from the knowledge of the excess specific heat. The values of δH were plotted as a function of ln(ta) and exhibit a linear behavior which indicates that the studied glasses were not completely relaxed.

Determination of kinetics parameters of glass transition in glassy Se and glassy Se98M2 alloys using DSC technique

Glassy Se and Se98M2 (M = Ag, Cd, Zn) alloys are obtained by the melt quenching technique. Differential Scanning Calorimetry (DSC) technique (under non-isothermal conditions) has been applied to see the effects of Ag, Cd, and Zn additives on the glass transition kinetics of Se-rich glassy alloys at different heating rates. The variation of glass transition temperature, Tg with the heating rate, β has been used to investigate the glass transition kinetics. The values of various kinetic parameters such as glass transition temperature, activation energy of glass transition, overall mean bond energy 〈E〉, heat of atomization HS, bond strength (Se–M) have also been calculated.

The Characterization and Study of Physical Parameters of Ge Modified Se-Sn-Pb Chalcogenide System

In the present paper, we have studied the effect of Ge addition on the physical properties of Se-Sn-Pb chalcogenide ma- terial. The necessary physical parameters which have important role in determining the structure and strength of the material viz. constraints, coordination number etc. have been calculated. The increasing trend has been found in cohesive energy, heat of atomization and mean bond energy. The glass transition has been studied using the Tichy-Ticha and Lankhorst approaches, which also increases with the increasing Ge contents. The increase in these physical parameters is due to the increasing covalent character in the material.

The Effect of Compositional Variation on Physical Properties of Te&amp;lt;sub&amp;gt;9&amp;lt;/sub&amp;gt;Se&amp;lt;sub&amp;gt;72&amp;lt;/sub&amp;gt;Ge&amp;lt;sub&amp;gt;19-X&amp;lt;/sub&amp;gt;Sb&amp;lt;sub&amp;gt;x&amp;lt;/sub&amp;gt; (X = 8, 9, 10, 11, 12) Glassy Material

The quaternary chalcogenide glass Te9Se72Ge19-xSbx (x = 8, 9, 10, 11, 12) has been prepared by the melt quench technique. The material fragility increases due to decrease in degree of cross linking in glass matrix as the Sb content increases. The heat of atomization decreases due to lower value of heat of atomization of antimony. The glass transition temperature is calculated by Tichy-Ticha and Lankhorst approaches. The glass seems to have high value of glass transition temperature as per theoretical calculations and is monotonically decreasing with increasing Sb content because increasing concentration of Sb reduces the cohesive energy and mean bond energy of the material.

Glass transition kinetics and optical band gap in Se 85− xSb 15Sn x ( x = 10, 11, 12.5, and 13) chalcogenide glasses

Se 85− x Sb 15Sn x (10 ≤ x ≤ 13) chalcogenide glasses were prepared by melt quenching technique. The glass transition temperature T g of the samples was recorded at different heating rates using differential scanning calorimeter DSC. From the heating rate dependence of T g, the activation energy for thermal relaxation E t was calculated using Moynihan model and Kissinger equation. It is found that T g increases with Sn content due to enhancement of both the degree of cross-linking parameter D cl and the mean bond energy of the average cross-linking per atom 〈 E cl〉. The observed increase in D cl and 〈 E cl〉 is attributed to the formation of SnSe 4/2 structural units of energies higher than that of Se–Se and Se–Sb bond energies. The decreasing trend of E t with the addition of Sn is an indication of improving thermal stability as it is also evident from the values of the temperature difference T c − T g. Correlation of T g values with the physical parameters of the studied glasses (for instance, the average coordination number 〈 Z〉, the average heat of atomization ( H s), the overall mean bond energy 〈 E〉, and the optical band gap ( E g)) reveals that T g increases linearly with 〈 Z〉, H s, and 〈 E〉 but the behavior with E g is opposite.

Compositional dependence of physical properties of ternary Se–Te–Bi alloys

Bulk samples of (Se100− x Bi x )90Te10 (x = 0, 0.5, 1, 1.5, 2, 2.5 and 3 at%) system were prepared using the melt quenching technique. The amorphous nature of bulk samples was confirmed using X-ray diffraction. The compositional variation in physical properties, namely density ρ, molar volume V m, compactness δ, average coordination number m, average number of constraints N con, number of lone pair electrons L, bond energy, average heat of atomization H s, mean bond energy ⟨E⟩ and glass transition temperature T g of the system have been studied. The mean bond energy has been calculated using the chemical bond approach (CBA). The glass transition temperature was calculated using the Tichy–Ticha method and was found to increase with Bi content. The mean bond energy was found to be proportional to the glass transition temperature. Average coordination number, average number of constraints, mean bond energy and density increase, whereas the average heat of atomization decreases with increasing Bi content in Se–Te alloys. The energies of the various possible bonds have also been determined.