Analysis of deep ion‐exchange behavior of Li₂ZnSiO₄ glass‐ceramics by experiments and machine learning

Transparent Li 2 O–ZnO–Al 2 O 3 –SiO 2 (LZAS) glass‐ceramics have excellent mechanical properties, which can be further improved through ion‐exchange. In this work, the transparent LZAS glass‐ceramics with the main crystalline phase of Li 2 ZnSiO 4 were ion‐exchanged in the mixed molten salts at varied temperatures and dwelling times, and their influence on the near‐surface structure and mechanical properties of glass‐ceramics were studied. The glass‐ceramic achieved the optimum comprehensive mechanical properties when ion‐exchanged with the mixed molten salts of 90 wt% NaNO 3 + 10 wt% KNO 3 . With the increasing in the ion‐exchange temperature ( T iox ) from 380 to 460°C, the optimal mechanical properties were achieved at 400°C, exhibiting a flexural strength of 432.5 MPa, a Vickers hardness of 7.9 GPa. At all the T iox , the depth of ion‐exchanged layer (DOL) remained above 130 µm, with the maximum value reaching ∼138.7 µm at 400°C. Upon the ion‐exchange, the surface crystalline phase did not change, which indicated that the ion‐exchange mainly occurred in the residual glassy phase. When ion‐exchanged in the 90 wt% NaNO 3 + 10 wt% KNO 3 molten salts, the calculated Na + diffusion coefficient initially increased and subsequently decreased with the increasing of the T iox . This behavior is attributed to T iox enhancing the impeding effect of K + on Na + diffusion. The ion‐exchanged glass‐ceramics subjected to a temperature of 430°C for 1.5 h exhibited the best drop resistance with no visible cracks after multiple drops from a height of 1.95 m. Machine learning was conducted on the ion‐exchange conditions, which predicted that a short exchanged time at relatively high T iox favored obtain a large DOL, which could effectively improve the drop resistance of glass‐ceramics.