Ternary GeAsS glasses have been investigated to determine the compositional
dependence of selected physical properties. Although the latter show a lin
ear variation with Ge:As ratio at a constant S content, many exhibit a nonl
inear dependence on the S content at a fixed Ge:As ratio. The trend of opti
cal properties tracks the increasing formation of metal-metal bonds as the
S concentration of these glasses is reduced below stoichiometry. Molar volu
me and thermal expansion coefficient display maxima near an average coordin
ation number of 2.6 for which there is no apparent indication in the Raman
spectra. The spectra of stoichiometric and S-excess glasses are dominated b
y a band at 345 cm(-1) due to the symmetric stretching of both AsS3 and GeS
4 groups; those of S-deficient glasses display bands associated with metal-
metal bonds between 210 and 240 cm(-1) whose intensity increase with increa
sing S deficiency. (C) 1999 Elsevier Science B.V. All rights reserved.