Investigation of zinc alkali pyrophosphate glasses. Part I: Development of low-Tg and high stability glasses

The zinc alkali pyrophosphate system has been investigated in order to produce glasses with low glass transition temperature (Tg < 400 °C) and high thermal and chemical stability. The (66-x)ZnO-xM2O-33.4P2O5 (with M = Na) composition line was first analysed to determine how the Zn2+/Na+ substitution impacts the macroscopic properties and glass stability. In a second time, the three alkali oxides Na2O, K2O and Li2O were mixed and used in combination with the optimum ZnO amount (46.6 mol%) to investigate the mixed alkali effect. Finally, comparison with other low Tg systems from the literature proves the relevancy of that system for the development of low-Tg and stable glasses.