Anneal-induced enhancement of refractive index and hardness of silicophosphate glasses containing six-fold coordinated silicon

摘要

A considerable number of optical devices have significantly benefited from the development of phosphate glasses as substrate materials. Introducing silica into sodium phosphate is an effective method to enhance its mechanical and optical properties. Through annealing treatment, the tetrahedral silicon oxide network structure (Si~((4))) can be transformed into an octahedral structure (Si~((6))) with more constraints. Here, we use high-temperature Raman and Nuclear Magnetic Resonance to reveal the mechanism of transformation between the Si~((4)) and Si~((6)) silicon oxide structures. The increase of the Si~((6)) content results in the phosphate glasses having higher refractive index and hardness. Based on this, the refractive index contribution of SiO_6 is obtained.