Short, intermediate and mesoscopic range order in sulfur-rich binary glasses

AbstractPulsed neutron and high-energy X-ray diffraction, small-angle neutron scattering, Raman spectroscopy and DSC were used to studystructural changes on the short, intermediate and mesoscopic range scale for sulfur-rich AsS x (x P 1.5) and GeS x (x P 2) glasses. Twostructural regions were found in the both systems. (1) Between stoichiometric (As 2 S 3 and GeS 2 ) and saturated (AsS 2.3 and GeS 2.7 ) com-positions, excessive sulfur atoms form sulfur dimers and/or short chains, replacing bridging sulfur in corner-sharing AsS 3/2 and GeS 4/2 units. (2) Above the saturated compositions at [As] < 30.5 at.% and [Ge] < 27 at.%, sulfur rings and longer sulfur chains (especially inthe AsS x system) appear in the glass network. The glasses become phase separated with the domains of 20–50 A˚, presumably enrichedwith sulfur rings. The longer chains S n are not stable and crystallize to c-S 8 on ageing of a few days to several months, depending oncomposition. 2005 Elsevier B.V. All rights reserved.