Preparation and characterization of new glassy system As2P2S8-Ga2S3.

Glasses having the composition (100 - x)As2P2S8-xGa2S3 with x ranging from 0 to 50% were investigated to determine the compositional effect on properties and local structure. The glass transition temperature (Tg) and the stability parameter against crystallization (Tx - Tg) increased with the addition of Ga2S3. The structure of these glasses was probed by Raman scattering, Fourier transform infrared (FT-IR) and 31P nuclear magnetic resonance. On the basis of the observed vibrations and the strength of the 31P-31P homonuclear magnetic dipolar coupling, two scenarios can be proposed for the structural evolution induced by the addition of Ga2S3. For x <or= 20% we may have the formation of GaS4E- groups (E = nonbonding electron), and for x >or= 30% we have depolymerization of the As2P2S8 units and the formation of a network of GaPS4 units with each PS 4/2 unit (Q4) species carrying a single positive formal charge.