SnO–P2O5 glasses have high refractive index and low glass transition temperature but have poor water durability. To improve water durability, NbO2.5 was added to SnO–P2O5 glasses, preparing SnO–NbO2.5–P2O5 glass. It was found that addition of only 4 mol % NbO2.5 was enough to achieve significant improvement of water durability, and at the same time, no degradation in thermal and optical properties was observed.
