Linking Melt Dynamics With Topological Phases and Molecular Structure of Sodium Phosphate Glasses From Calorimetry, Raman Scattering, and Infrared Reflectance

摘要

A score of especially dry and homogeneous (Na2O)x(P2O5)100-x glass compositions over a wide range, 0 50%), Tg(x) mildly decreases with increasing x, as pyrophosphate units decouple from the backbone and glasses segregate. Raman scattering measurements show that the fraction of the local structural species, f(Q3(x)), f(Q2(x)) and f(Q1(x)) track the mean-field behavior based on glass stoichiometry (x), as noted earlier from 31P NMR experiments. Raman scattering also shows that the Q2 structural species always display a triad of modes, a majority mode and two satellite modes that serve as topological defects. For the two highest frequency optic modes, Infrared specular reflectance measurements show that the frequency difference between the Longitudinal Optic (LO) and Transverse Optic (TO) response displays a global minimum in the IP. The local minimum of molar volumes, a global minimum in the LO-TO mode splitting, a fragility window that coincides with the reversibility window, each observation provides persuasive evidence of the singular role of the IP in present glasses.