Indentation‐induced Structural Adaptability in Highly Crack‐resistant Metaluminous Alkali Aluminoborate Glasses

Improving the crack resistance (CR) in oxide glass remains a significant challenge in the field of damage tolerance, particularly in scenarios involving sharp contact loading. In this study, lithium‐, sodium‐, and potassium‐aluminoborate glasses with compositions ranging from 50 to 80 mol.% B 2 O 3 were prepared to investigate the interplay between composition, elastic properties, and structural rearrangements under indentation. Density, elastic moduli, and Vickers hardness were measured, and the CR was determined. Micro‐Raman spectroscopy investigations were conducted on both pristine surfaces and within residual indents in order to characterize stress‐induced structural changes. A significant enhancement in CR is observed as the cationic field strength of the modifier cation is decreased and the alumina content is increased, reaching a maximum CR value of 51.5 N for the potassium‐rich compositions. Raman scattering results reveal changes consistent with stress‐induced borate‐network reorganization, including boroxol‐ring disruption, the formation of non‐ring borate units and units containing non‐bridging oxygens, and suggest changes in boron coordination. In all glass series, samples exhibiting the highest CR also displayed the maximum load‐induced shift of κ, defined as the barycenter of the borate‐unit region. The findings suggest that the glass network's ability for structural reorganization, particularly alterations in the boron environment, is key to augmenting the CR. The cooperative effect between boron and aluminum units appears to promote stress accommodation at indentation sites, providing new insights for the design of damage‐resistant oxide glasses.