Meeting experimental challenges to physics of network glasses: Assessing the role of sample homogeneity

We introduce a Raman profiling method to track homogenization of GexSe100-x melts in real time, and show that 2 g melts reacted at 950 degrees C in high vacuum homogenize in 168 h on a scale of 10 mu m. Homogenization of melts is precursive to self-organization of glasses. In the present glasses, compositional variation of Raman active corner-sharing mode frequency of GeSe4 units, molar volumes, and the enthalpy of relaxation at T-g, reveal the rigidity (x(c)(1) = 19.5(3)%) and the stress (x(c)(2) = 26.0(3)%) transitions to be rather sharp (Delta chi < 0.6%). These abrupt elastic phase transitions are in harmony with rigidity theory and have a direct bearing on the physics of glasses. (C) 2011 Elsevier Ltd. All rights reserved.