Tantalum-lanthanum mixing effect on structural and mechanical properties of aluminate glasses

Aluminate glasses are known for their superior mechanical and optical properties. Here, we investigated the tantalum (Ta)-lanthanum (La) mixing effect on structural and mechanical properties of these glasses. Using the aerodynamic levitation and laser melting technique, we prepared a series of aluminate glasses with the molar composition 54Al₂O₃·(46-x)La₂O₃·xTa₂O₅, where x = 0.0, 9.2, 18.4, 23.0, 32.2, 36.8, and 46.0. The structural, thermal, and mechanical analyses revealed that substituting Ta for La strongly impacted the local Al environment in the glasses, thereby affecting their glass transition temperature and mechanical properties. The Vickers microhardness (H_V) varied non-monotonically with the molar ratio R (defined as Ta/(Ta+La) = x/46), reaching a maximum H_V value of 8.59 GPa at R = 0.8. This trend was explained in terms of both the average bond energy and the bond number density. Moreover, the crack initiation resistance of the studied glasses increased as R rose. This work aids in the design of oxide glasses with high crack resistance and hardness.