Abstract: Understanding the relationship between structure and performances such as hardness and crack resistance has guiding significance for the development of the hard and highly crack resistant glass. To study the structural dependence of hardness and crack resistance on composition in the CaO-Al₂O₃ pseudo-binary glass system, utilizing the laser-heated aerodynamic levitation method, a series of xCaO·(100-x)Al₂O₃ glasses were prepared with x=42.3, 50.0, 63.1, and 75.0, mole fraction. The Vickers hardness (H_V) and crack resistance (C_R) were studied by using a micro-hardness Vicker tester. The structure of these glasses was characterized by Raman spectra, X-ray diffraction (XRD) patterns and magic angle spinning nuclear magnetic resonance (MAS-NMR). The results indicate that with the increase of the CaO content, the H_V values of these glasses decrease whereas the C_R values show a non-linear and non-exponential change. The 42.3CaO·57.7Al₂O₃ glass exhibits the maximum values of H_V (8.09 GPa) and C_R (11.8 N). The decrease of H_V values upon the addition of CaO is attributed to the decrease of average bond energy. The maximum C_R value of the 42.3CaO·57.7Al₂O₃ glass is ascribed to the existence of five coordinated Al, which dissipates the energy in the indentation process through changing the coordination number.

Key words: calcium aluminum glass, aerodynamic levitation method, laser heating, hardness, crack resistance, coordination environment