Abstract: To explore the evolution law of crack initiation resistance (C_R) in ZnO·Al₂O₃·nSiO₂ (n=2, 2.35, 2.5, 2.65, 3, 3.5) glasses varies with SiO₂ content, series of glass samples were prepared by the conventional melt-quenching method. By characterizing C_R and the microstructure of these aluminosilicate glasses in detail, the results shows that an abnormal evolution that C_R increases first and then decreases with the increase of SiO₂ content, and arrives the maximum value of 31.1 N at n=2.5. With the increase of n: (1) the atomic packing density decreases gradually, which induces the increase in C_R due to the increase in volume available for densification; (2) the quantity of Al—O polyhedra decreases, which leads to the drop in C_R due to the higher damage resistance of Al—O polyhedra compared to the SiO₄ units; (3) considering the strong retarding upon crack initiation originated from phase interfaces, the non-monotonic change in the quantity of phase interfaces induces the corresponding abnormal evolution in C_R for the aluminosilicate glasses. The competition and synergy of the above three factors are the structural origin of the abnormal evolution of C_R in this system. Finally, considering the insignificant change in composition near the maximum value, the non-monotonic change in the quantity of phase interfaces varies with n should be the main structual origin of the abnormal evolution in C_R.

Key words: zinc aluminosilicate glass, crack initiation resistance, glass structure, atomic packing density, Al—O polyhedron, phase interface