Deformation and structural densification in Al2O3–Y2O3 glass

In this article, we examine the unusual plastic deformation under uniaxial compression of an Al2O3–15 mol.% Y2O3 (A15Y) glass synthesized by a wet chemical route. At a low temperature of 650–725 °C, plastic deformation of this glass is largely non-viscous through shear instabilities. In contrast, deformation near the crystallization temperature (850 °C) occurs homogeneously with work hardening and with a monotonic increase in the true density of the glass by 10–12%, accompanied by an increase in hardness (H) and elastic modulus (E) of up to 100%. We hypothesize a phenomenon of molecular densification of the amorphous structure through a hierarchy of multiple phases, analogous to density- or entropy-driven amorphous-to-amorphous phase transitions (polyamorphism). These results suggest that the present method of preparation and the unusual behavior can trigger a search for many more systems that display such behavior.