Synthesis of hyperordered permanently densified silica glasses by hot compression above the glass transition temperature

Abstract

Synthesizing densified glasses with structure ordering is an important issue for the development of new optical fibers with high refractive index and low dispersion. Herein, we report on our attempt to synthesize densified silica (SiO₂) glasses by hot compression at a pressure of 7.7 GPa and temperatures above 1200 °C. We succeeded for the first time in recovering densified SiO₂ glasses compressed at 7.7 GPa and 1300 °C. Samples compressed above 1300 °C were crystallized into coesite by heterogeneous nucleation. The height of the first sharp diffraction peak in high-energy X-ray and neutron diffraction data of densified SiO₂ glasses increased with increasing temperature, indicating the evolution of intermediate-range ordering. Furthermore, the density increase of hot-compressed SiO₂ glasses was estimated by analyzing reduced pair distribution functions. We found that the SiO₂ glass compressed at 7.7 GPa and 1300 °C is by far the most densified and structurally ordered (hyperorderd) glass in the world.