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

Abstract Homogeneous germanium oxy-sulfide (1 − x )GeS 2 – x GeO 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 GeO 2 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 GeO 2 to GeS 2 glass causes the transformation of GeS 4/2 units to mixed oxy-sulfide GeS 3/2 O 1/2 , GeS 2/2 O 2/2 , and GeS 1/2 O 3/2 structural units at progressively higher GeO 2 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 g are not fully understood, although other common examples of such non-linear behavior are well known in simple binary alkali silicate glasses.