Pressure-induced transformations in a glass: In situ X-Ray diffraction and Raman spectroscopy

This study investigated the amorphous structure of a soda-lime-silicate glass sample (Na2O·2CaO·3SiO2) utilizing in situ X-ray diffraction and Raman spectroscopy at pressures up to 30.3 GPa. These techniques provided insights into the structure of the glass under high pressure. Analysis of the short-range order of the glass in function of pressure was obtained from the pair distribution function, obtained from the diffractograms, and uncovered the emergence of a new amorphous phase at ∼10 GPa, identifiable through the appearance of new peaks in the data beyond this pressure value. Simultaneous measurements from Raman spectroscopy identified the elastic limit of the material at ∼6 GPa and were used to measure the inter-tetrahedral ∠Si–O–Si angle, which also displayed a ∂θ/∂P discontinuity within the 10 GPa range, due to the new amorphous phase. The study emphasized the potential of utilizing a monolithic glass sample within a diamond anvil cell, highlighting its ability to produce a sufficiently intense diffraction signal for structural analysis of glassy samples, provided that the angular aperture and energy employed are sufficiently high.