Structure and properties of NaPO3–ZnO–Nb2O5–Al2O3 glasses

In an effort to design low-melting, durable, transparent glasses, two series of glasses have been prepared in the NaPO3–ZnO–Nb2O5–Al2O3 system with ZnO/Nb2O5 ratio of 2 and 1. The addition of ZnO and Nb2O5 to the sodium aluminophosphate matrix yields a linear increase of properties such as glass transition temperature, density, refractive index and elastic moduli. The chemical durability is also significantly, but nonlinearly, improved. The glass with the highest niobium concentration, 55NaPO3–20ZnO–20Nb2O5–5Al2O3 was found to have a dissolution rate of 4.5 × 10− 8 g cm− 2 min− 1, comparable to window glass. Structural models of the glasses were developed using Raman spectroscopy and nuclear magnetic resonance spectroscopy, and the models were correlated with the compositional dependence of the properties.