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Chalcogenide glasses in the Na2S–GeS2–Ga2S3pseudoternary system were synthesized using a combination route of melt-quenching and mechanical-milling methods. First, a glass rich in germanium (90GeS2–10Ga2S3) is synthesized by melt-quenching synthesis in a silica tube sealed under vacuum. This glass is used as a precursor for the second step of mechanochemistry to explore the Na2S–GeS2–Ga2S3pseudoternary system. By using this synthesis route, the glass-forming ability is improved as the vitreous domain is enlarged, especially for Na- and Ga-rich compositions. The as-obtained amorphous powders are characterized by Raman spectroscopy, differential scanning calorimetry, X-ray total scattering, and pair distribution function (PDF) analysis. The evolution of the Raman features observed is reproduced using density functional theory calculations. Impedance spectroscopy was performed to determine the conductivity of the new glasses. The addition of germanium sulfide to the Na2S–Ga2S3pseudobinary system enables one to increase the conductivity by 1 order of magnitude. The highest room-temperature ionic conductivity, as measured by impedance spectroscopy, is 1.8 × 10–5S·cm–1.

NaGaS2is a newly discovered compound that has already shown great promise for a variety of applications because of its layered structure and ion exchange properties. In this work, crystalline NaGaS2has been synthesized by an alternative method to what has been previously published, namely, by mechanochemistry, either by a direct one-step process or by a two-step process. In the one-step process, crystalline NaGaS2is directly formed by milling sodium sulfide Na2S and gallium(III) sulfide Ga2S3. However, an amorphous material is present in majority together with the crystalline phase. In the two-step process, amorphous NaGaS2is first obtained by mechanical milling and then heated above its glass transition temperature to obtain a glass–ceramic mainly composed of crystalline NaGaS2. For the two-step process, changes of the local atomic-level structure in amorphous NaGaS2and after crystallization were analyzed by high-field solid-state nuclear magnetic resonance (NMR) spectroscopy as well as by X-ray total scattering and pair distribution function (PDF) analysis. Based on quantitative analysis on the 23Na NMR spectra, modifying the annealing treatment can promote the formation of the crystalline phase up to a molar fraction of 83.8%.

The structure of the binary chalcohalide glasses Te1–xClx(0.35 ≤ x≤ 0.65) is considered by combining experimental and theoretical results. The structural network properties are influenced by a competition between ionic and covalent bonding in such glasses. At first, a focus is placed on the detailed information available by using the complementary high-energy X-ray and the neutron diffractions in both the reciprocal and real spaces. The main characteristic suggested by the structure factors S(Q) concerns the presence of three length scales in the intermediate range order. The total correlation function T(r) lets us also suppose that the structure of these glasses is more complicated than Te-chain fragments with terminal Cl as demonstrated in crystalline Te3Cl2. Molecular dynamics simulations were subsequently performed on Te3Cl2and Te2Cl3, and coupled with the experimental data, a highly reticulated network of chalcogen atoms, with a fair amount of chlorine atoms bonded in a bridging mode, is proposed. The simulations clearly lead to a glass description that differs markedly from the simple structural model based on only Te atom chains and terminal Cl atoms. Solid-state NMR experiments and NMR parameters calculations allowed validation of the presence of Te highly coordinated with chlorine in these glasses.