Zhiyu Wang

The effects of Sn and Bi additions on properties and structure in Ge-Se-Te chalcogenide glass

Abstract The effects of Sn and Bi additions on the properties and structure in Ge 2 Se 5 Te 3 glass have been studied by X-ray diffractometry, differential thermal analysis (DTA), analysis of weight-loss in solution, infrared (IR) transmission spectra and far Fourier-transform infrared (far FTIR) spectra for the purpose of expanding the IR transparency region of the Ge-Se-Te system glass and to decrease the fibres attenuation at 10.6 μm. The additional Sn atom, which has formed [SnSe 4 ] tetrahedra, another type of network former in the glass network, increased the glass transition and crystallization temperatures, T g and T c , respectively, anti-crystallisation stability, chemical durability and IR multiphonon edge. The optimum glass composition in this quaternary system has a quantitative ratio (mol) of Ge/Sn ≈ 2. The most outstanding advantages of the Ge-Se-Te-Bi glass system are its excellent chemical durability and broad IR transparency region (the multiphonon absorption edge has been extended to 17.6 μm, 1.2 μm longer compared with the Ge-Se-Te system glass). Meanwhile, other properties of this glass are still somewhat better than the original Ge-Se-Te glass. These two chalcogenide glasses are candidates for drawing fibres for far-infrared transmission, especially for CO 2 laser radiation (10.6 μm) delivery in various environments.

Structure and some physical properties in relation to average co-ordination number, 〈r〉, in TeX and TeXAs glasses

Abstract Vibrational spectra and differential scanning calorimeter analysis of glass structure, transition temperature, Tg, and heat capacity jump, ΔCp, at Tg indicate that the new glasses in the Te Se As system can be divided into two groups. The first, ‘TeX’-type glass, with the average coordination number, 〈r〉 Te chains principally, and the fraction of chains containing As atoms is negligible. Some Physical properties of this glass, such as Tg, ΔCp and thermal expansion coefficient, α, etc., deviate from the universal linear function of 〈r〉 advanced for covalent bonding inorganic glasses with networks consisting of long polymer chains, because of the existence of Se8 rings and Te I Te groups in the glass network. The second As-rich ‘TeXAs’-type glass, with the average coordination number, 〈r〉 > 2.2, has a two-dimensional glass network by the cross-linkages between Se Te As chains through As As bonds. No Se8 rings and two-coordinated I atoms exist in this glass because of the formations of [AsSe3] pyramids and As I bonds. The physical properties of this glass have an excellent agreement with the topological linear function of 〈r〉 as in the Ge As Se system, and they are optimized at the Phillips-Thorpe rigidity percolation threshold value, 〈r〉 = 2.4.