Thermally reversing window and stiffness transitions in chalcogenide glasses

Raman scattering and temperature-modulated differential scanning calorimetry measurements on SixSe1-x glasses show that onset of rigidity occurs over a wide compositional window 0.20 < x < 0.27 across which glass transitions are found to be thermally reversing in character. There is a ten-fold reduction in the non-reversing heat flow at the transition within the window in relation to that outside the window. The large compositional width associated with the onset of rigidity in this chalcogenide glass is in sharp contrast to the solitary transition predicted by mean-field constraint counting and by existing numerical simulations in random networks. (C) 1999 Elsevier Science Ltd. All rights reserved.