Processing and characterization of new oxy-sulfo-telluride glasses in the Ge–Sb–Te–S–O system

New oxy-sulfo-telluride glasses have been prepared in the Ge–Sb–Te–S–O system employing a two-step melting process which involves the processing of a chalcogenide glass (ChG) and subsequent melting with TeO2 or Sb2O3. The progressive incorporation of O at the expense of S was found to increase the density and the glass transition temperature and to decrease the molar volume of the investigated oxy-sulfo-telluride glasses. We also observed a shift of the vis–NIR cut-off wavelength to longer wavelength probably due to changes in Sb coordination within the glass matrix and overall matrix polarizability. Using Raman spectroscopy, correlations have been shown between the formation of Ge- and Sb-based oxysulfide structural units and the S/O ratio. Lastly, two glasses with similar composition (Ge20Sb6S64Te3O7) processed by melting the Ge23Sb7S70 glass with TeO2 or the Ge23Sb2S72Te4 glass with Sb2O3 were found to have slightly different physical, thermal, optical and structural properties. These changes are thought to result mainly from the higher moisture content and sensitivity of the TeO2 starting materials as compared to that of the Sb2O3.