Doping of low-Tg phosphate glass with Al₂O₃, B₂O₃ and SiO₂: Part I- effect on glass property and stability

A zinc alkali pyrophosphate system 46.6ZnO-20Na2O-33.5P2O5 presenting low-Tg (339 °C) and good thermal stability has been doped with (1–4) mol% of Al2O3, B2O3 and SiO2 to improve the stability of the glass with a minimal increase in glass transition temperature (Tg).XRD and 1D 31P solid state NMR were used to monitor the isothermal crystallization process occurring at 130 °C above Tg. If the Al2O3 and B2O3 doping significantly improved thermal stability, this property was marginally affected by SiO2 doping. Viscosity measurements were performed to observe the crystallization effects induced by the doping. It is noteworthy that the Tg values of all the doped compositions with improved stability presented in this work are below 400 °C.Raman spectroscopy, 1D 31P, 27Al, 11B and 29Si solid state NMR were carried out to determine the structural modifications and coordination states of the doping elements all along the composition line