Micro-structural studies of GeSe2–Ga2Se3–MX (MX = CsI and PbI2) glasses using Raman spectra

Microstructure of the chalcohalide glasses: GeSe2–Ga2Se3–CsI and GeSe2–Ga2Se3–PbI2 ternary system were investigated by Raman spectra, lifetime of Dy3+ infrared emission and glass transition temperature (Tg). The evolution of the Raman spectra shows that the fundamental structural groups of these studied glasses consist of [Ge(Ga)Se4] tetrahedral and some complex structure units [Ge(Ga)IxSe4−x](x = 1–4). The x value varied when the different iodide was added in Ge–Ga–Se matrix. For GeSe2–Ga2Se3–CsI glasses, the [Ge(Ga)IxSe4−x](x = 1–4) mixed-anion tetrahedral and [Ga2I7]− units occurred. For GeSe2–Ga2Se3–PbI2 glasses, the [Ge(Ga)I2Se2], [Ge(Ga)I3Se] units can be formed. The changes of Dy3+ infrared emission lifetime and Tg support the results. Additionally, [PbIn] structural units will be formed in GeSe2–Ga2Se3–PbI2 glasses due to high form-ability of these units when the PbI2 content is high.