Influence of vapor-phase reaction on the reduction of OH?and S–H absorption bands in GeS2-based glasses for infrared optics

Abstract

The reduction of OH- and S–H absorption bands in unary and ternary germanium sulphide glasses with oxides and hydroxides present in the raw materials and in impure glasses was studied via the chemical reaction of H2and HCl gases at high temperatures. Multicomponent phase equilibria calculations in the Ge–S–H–O–X (X = Cl, I) system were performed to determine the equilibrium partial pressures of gaseous species for removing oxygen and hydrogen from the glasses used for infrared (IR) applications. The effect of carbon on the reduction in oxide and hydroxide absorption bands was also investigated. The absorption characterization was carried out using a Fourier transform infrared reflection spectrophotometer. The IR absorption bands between 1000 and 3700 cm-1 were identified and analyzed. The Boson peaks (BP) in glass samples with two different OH- concentrations were also analyzed. It was found that the presence of OH- enhanced the intensity of Boson peaks. The sites for OH- and shared oxygen with the main [GeS4] 4- tetrahedron structural units in the glass are discussed with respect to the BP and IR absorption analyses. The structure model also identifies the origin of the reduced Rare-earth (RE+3 ) ion solubility (in particular Pr 3+ ions) and its dependence on OH- ion concentrations in GeS2 glasses