Influence of iso-structural substitutions on properties in Ge(Sb,As)(S,Se) glasses

1. S2/2Sb-SbS2/2 + SbSe3/2 GeSe4/2 G. Guery, J.D. Musgraves1, E. Fargin2, K. Richardson1 1. School of Materials Science and Engineering, Clemson University, Clemson, SC 29634, USA 2. Institut de Chimie de la Matiere Condensee de Bordeaux, France Optical Properties S3/2Ge-SbS2/2 + GeSe4/2 OBJECTIVE To predict evolutions of glass properties in Ge28Sb12S60-xSexand Ge28As12S60-xSexglasses with x = 0, 15, 30, 45 and 60. Ge2Se2Se4/2 GeS4/2 1) Ultra Violet – Visible Spectroscopy GeS4/2 INTRODUCTION Thermal Properties Ge2S2S4/2 Ge2S2S4/2 Choice of Materials: Chalcogenide glass (ChGs) 1) Differential Scanning Calorimetry Development of new chalcogenide glasses for novel IR aspherical lenses using Precision Glass Molding (PGM). AsSe3/2 + As2S4/2 • Exceptional infrared transparency • Large linear refractive index • Low phonon energy •  ~ 4.5 g/cm3, n~ 2.5 (in the IR) • ΔT > 100°C  good stability against crystallization during molding. • Tg ↓ when Se ↑ because selenide bonds are weaker  need less thermal energy (kT) to disrupt bonding. • As system has higher overall Tg than Sb system • Plateau in Tg change in the 30-45 mol% region – change in dominant bonds check by Raman spectroscopy . This project specifically examines glass properties for PGM. Influence of iso-structural substitutions on properties in Ge(Sb,As)(S,Se) glasses • When Se increases shift of the band gap to higher wavelengththe due to electronic density. • No major absorption at λ> 1000 nm  Transparent in the IR. • Absorption at λ <1000 nm  Opaque in the UV-Vis. Physical Properties 1) Density 2) Viscosity using parallel plate viscometer 2) Fourier Transform Infrared Spectroscopy • ρ↑ when Se ↑ because MSe > MS. • ρSb > ρAs because MSb> MAs. 2) Microhardness • r(Se) > r(S), so E(Se bonds) < E(S bonds); when Se increases, log(viscosity) decreases. • Multiple absorption bands related to oxide and hydroxide impurities. • Sulfur is more hygroscopic than selenium  peaks due to humidity in air are more important in sulfide glass than selenide glass. • Impurities in the material reduce the glass transparency at specific wavelengths. SH As-O SH Se-O/S-O Structural Properties – Raman Spectroscopy Ge-O Ge-O H2O • Hv↓ when Se ↑ due to the strength of the bonds. Se-H OH H2O H2O OH 3) Coefficient of Thermal Expansion CONCLUSION By substitution of S for Se or Sb for As, we can predict and obtain different physical, thermal, optical and structural properties. • <CN>=2.68=constant due to iso-structural substitution, so no change in CTE is expected. • 0<X<30: Ge28Sb12S60-xSex preferentially dominated by Ge-Se bonds. Ge28As12S60-xSex preferentially dominated by As-Se bonds. • 30<X<60: Ge28Sb12S60-xSex preferentially dominated by Sb-Se bonds. Ge28As12S60-xSex preferentially dominated by Ge-Se bonds. Acknowledgements: Work supported in part by the EU and US Department of Education (P116J080033) MILMI Dual-Master program between Clemson University and University of Bordeaux I, Department of Chemistry. Special thanks to Laeticia Petit and the GPCL Group.