The morphology and composition of nanosized amorphous-phase separation in the Y2O3–Al2O3–SiO2 glass system

A systematic experimental study of the Y2O3–Al2O3–SiO2 (YAS) compositional system has been carried out with a focus on nanoparticle formation in the high SiO2 region, where nanoscale phase separation occurs. The unique capabilities of the aerodynamic levitation coupled to the laser-heating method have been exploited and compared to conventional melt-quenching. This systematic study has mainly focused on the region where melting temperatures exceed 1700 °C, which is the maximum temperature commonly available for the preparation of glass by conventional melt-quenching. The feasibility and the effect of the two synthesis routes on the preparation of glass samples have been compared. The prepared samples were characterised by X-ray diffraction, differential scanning calorimetry, Raman spectroscopy, and scanning and transmission electron microscopy. It is evident from the results that in the part of the phase diagram with SiO2 content above 65 mol% and simultaneously Y2O3 content below 17.5 mol%, the phase separation has led to the formation of amorphous SiO2 nanoparticles. It has been shown that the size and distribution of the nanoparticles can be controlled not only by the chosen technology but also by changing the starting composition.