Structure and properties of off-stoichiometric Ba–Ga–Ge selenide glasses

• Published in: Journal of non-crystalline solids Vol. 427; pp. 62 - 68
• Main Authors: Mao, A.W., Kaseman, D.C., Aitken, B.G., Sen, S.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01-11-2015
• Subjects: BaSe–Ga2Se3–GeSe2 ± Se; Chalcogenides; Chalogenide glass; Covalence; Density; Evolution; Formations; Glass; NMR spectroscopy; Properties; Selenides; Spectroscopy; Structure; Spectroscopy; BaSe–Ga2Se3–GeSe2±Se; Structure; Properties; Chalogenide glass
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2015.07.023

Off-stoichiometric glasses in the Ba–Ga–Ge–Se system with Se excess or deficiency (BGGS±Se) are synthesized and their structure is characterized using Raman and multinuclear (77Se, 71Ga) magic-angle-spinning nuclear magnetic resonance (MAS NMR) spectroscopy. The results reveal that the structure of these off-stoichiometric BGGS±Se glasses consists of a charge-compensated, partially covalent network of corner-sharing (Ga/Ge)Se4 tetrahedra where [GaSe4]− tetrahedra charge balance the Ba2+ cations. Addition of excess Se to a stoichiometric BaSe–Ga2Se3–GeSe2 glass with BaSe:Ga2Se3>1 results in the formation of Se–Se linkages, while Se deficiency is accommodated via the formation of homopolar Ge–Ge bonds, in agreement with the continuously-alloyed structural scenario of purely covalent chalcogenide glasses. Such composition-dependent structural evolution is shown to be consistent with the corresponding variation in density and glass transition temperature.
•Atomic structure of off-stoichiometric glasses in the system Ba–Ga–Ge–Se is studied.•Raman and multinuclear NMR spectra, density, and Tg are reported.•Stoichiometry plays an important role in controlling the mode of Se incorporation.•Network shows characteristics of charge-compensated and continuously alloyed scenarios.