Mechanical properties of hydrated cesium-lithium aluminoborate glasses

Elastic moduli, fracture toughness, crack initiation resistance, and hardness are four important mechanical properties of oxide glasses. However, the correlation between them as well as their relations to glass composition and extrinsic factors are not yet fully understood. In this study, we investigate the variations in these mechanical properties in mixed Cs2O/Li2O-aluminoborate glasses, which are subjected to aging in a humid atmosphere. We observe pronounced nonlinear scaling of the mechanical properties due to the mixed alkali effect, and following the surface hydration, we observe an increase in crack resistance and a decrease in Vickers hardness. These variations are explained by Raman spectroscopy data collected at different depths within the hydrated surface. We found no clear relations between Vickers hardness, crack resistance, and fracture toughness, although Vickers hardness appears to increase and crack resistance appears to decrease with increasing fracture toughness for the present glass series. The glass with equal contents of Cs and Li provides the best compromise between high fracture toughness and Vickers hardness and with a potential to increase the crack resistance through humid aging.