Physical and mechanical properties of ternary Ge-Se-Sb glasses for near-infrared applications

Abstract

Many physical properties such as the average coordination number (CN), the compactness (δ), the overall bond energy (〈E〉), the cohesive energy (CE), the mean bond energy (E s), and the overall electronegativity difference (Δχ) as well as the degrees of ionicity (Ion) and covalency (Cov) were estimated theoretically. The chemical bond approach (CBA) was used to predict the type and proportion of the formed bonds in the studied glasses. Consequently, several structural and physical properties have been estimated. The results show that the studied glasses are rigidly connected, having an average coordination number increase from 2.41 to 2.61. Two approaches have been successfully used to estimate the band gap (E g) theoretically compared with the previously published experimental values for the Ge18Se82−xSbx (5 ≤ x ≤ 25 at. %) glasses. Values of E g decrease from 1.59 to 1.15 eV by an increase of the Sb content from 5 to 25 at. %. i.e. the wavelengths corresponding to E g values lie in the near-infrared range of spectra, which make these glasses candidates for the near-infrared applications. Furthermore, the ultrasonic longitudinal (v L ) and shear wave (v T ) velocities propagating through the glasses have been used to estimate the mechanical parameters such as the elastic bulk modulus, Poisson’s ratio, Young’s modulus, micro-hardness, and temperature of Debye. It was found that a change in slope occurs for various physical, mechanical, and structural properties near the stoichiometric composition (x ≈ 18 at. %) at which the glass structure consists of heteropolar bonds only.