High‐Pressure Effects on Oxide Glasses: I, Densification in Rigid State

Densification of SiO 2 , GeO 2 , and B 2 O 3 glasses in the rigid state was studied at pressures up to 80 kb and at temperatures up to 600°C in different pressure‐transmitting media. The infrared, ultraviolet, and nuclear magnetic resonance absorptions of the compressed glasses were examined. Densification increased with time, temperature, pressure, and more important, with applied shear. This process of volumetric shrinkage in the rigid state at low temperatures is fundamentally different from that at temperatures at or above the glass transition. A qualitative model involving mutual entanglement of parts of the random glassy network is postulated to explain the observed results.