Preparation and characterization of germanium oxy-sulfide GeS2-GeO2 glasses

Homogeneous germanium oxy-sulfide (1 - x)GeS2-xGeO(2) glasses were prepared from 0 <= x <= 1 by rapidly quenching melts to room temperature showing no evidence of phase separation all across the compositional range. A non-linear variation of the glass transition temperature (T-g) was observed where T-g increased initially with small amounts of GeO2 up to x = 0.1, remained approximately constant over the range of 0.2 <= x <= 0.8, and then increased again at the end of glass forming range (x >= 0.8). Bridging Ge-S-Ge and Ge-O-Ge vibrational stretching modes were observed in both the Raman and Infrared spectra. Bending modes of the S-Ge-O linkages were also observed in the Raman spectra. From these results, it is suggested that the addition of GeO2 to GeS2 glass causes the transformation of GeS4/2 units to mixed oxy-sulfide GeS3/2O1/2, GeS2/2O2/2, and GeS1/2O3/2 structural units at progressively higher GeO2 contents. While the structure of these glasses apparently changes continuously and smoothly with composition, the non-linear changes in the physical properties like the T, are not fully understood, although other common examples of such non-linear behavior are well known in simple binary alkali silicate glasses. (c) 2005 Published by Elsevier B.V.