The effect of Te on the physical properties of GeAsS glasses

Stoichiometric, chalcogen-excess and chalcogen-deficient As-rich GeAs sulphotelluride glasses were synthesized. Liquid immiscibility was observed for glasses containing 40%, 0% (stoichiometric) and -30% excess chalcogen, whereas -60% excess chalcogen glasses were homogeneous at all S:Te ratios. For stoichiometric glasses, the two immiscible phases formed an emulsion-like microstructure and were As-, Te-rich on the one hand, and Ge-, S-rich on the other with respect to the bulk composition. In -30% excess chalcogen glasses, the worm-like microstructure of the two glasses was continuous throughout the region of immiscibility. Although the scale of the phase separation in the latter was submicroscopic, its presence was revealed by a red shift of the absorption edge of these glasses, and by anomalies in the compositional dependence of the electrical resistivity, the glass transition temperature and the softening point. (C) 2003 Elsevier B.V. All rights reserved.