Pressure-induced amorphization of a combeite crystal

Abstract

This study explored the Combeite crystal (Na2O·2CaO·3SiO2) under high-pressure conditions. This crystal was initially produced by fully crystallizing a glass with the same composition. A diamond anvil cell was used to analyze the crystal under pressures up to 30 GPa by performing in situ X-ray diffraction and Raman spectroscopy. The results show a densification up to 10.3 GPa, which can be seen on the shifts on the peaks of the diffractograms, as well as the same behavior being observed in the Raman spectra up to the same pressure value. Starting at that point and ending at 15.5 GPa, the material undergoes a transition characterized by the disappearance of all Combeite peaks from the diffractograms as well as a huge jump in the full width at half maximum of the main Raman band; both results indicate that this crystal undergoes a pressure-induced amorphization. This conclusion is corroborated by comparing the results from this study to the parent glass under the same high-pressure conditions, where it can be observed that the structures obtained, at 30 GPa, both exhibit an amorphous structure, regardless of whether they originated from the glass or the Combeite crystal.