Viscosity and Softening Behavior of Alkali Zinc Sulfophosphate Glasses

摘要

We report on the softening properties and viscosity of glasses from the system ZnO-Na_2O-SO_3-P_2O_5 for low-temperature sealing applications. Up to a ratio of network-forming ions PO_4~(3-):SO_4~(2-) of about 2:1, a gradual substitution of P_2O_5 by SO_3 results in decreasing glass transition and softening temperatures. At the same time, decreasing kinetic fragility is observed, noteworthy even for decreasing the total amount of network former from 44 at.% to 39 at.%. Thermomechanical and ca-lorimetric analyses reveal a distinct SO+4~(2-) -promoted relaxation phenomenon at temperatures significantly below the macroscopic glass transition temperature, which is interpreted as a result of the formation of an increasingly interconnected assembly of SO_4~(2-) and PO_4~(3-) units with increasing SO_3 content.