Structural design of a scalable glass with high hardness and crack initiation resistance

The industry has always strived to design “hard” and “crack-resistant” glass. However, simultaneously realizing these properties in oxide glasses has been rare. Although Al₂O₃-rich hard and crack-resistant oxide glasses have been reported in the last decade, they exhibit two significant technological challenges that hinder their translation from laboratory to industry: (1) high processing temperatures (>2000 °C) and (2) small glass-forming regions (near eutectic). The present study reports the structural design of a hard and high modulus glass with high crack initiation resistance designed in the peraluminous region of rare-earth containing MgO–Al₂O₃–B₂O₃–SiO₂ system. The glass can be processed at a temperature ≤1650 °C and exhibits Vickers hardness (H_v) of 7.84 GPa (at 1.96 N load) and indentation crack resistance (ICR) of 26.5 N. These H_v and ICR values are significantly higher than most commercial or non-commercial glasses (prior to thermal tempering, densification near T_g, or chemical strengthening). The glass has been scaled up to successfully produce slabs of dimensions 100 mm × 100 mm × 8 mm at laboratory scale with optical transmission of 90 ± 2 %. The results presented here are scientifically intriguing and have considerable tangible implications, as they pave the path for the design and development of stronger glasses for functional applications.