Balancing fracture toughness and transparency in barium titanosilicate glass-ceramics

Tough and hard, yet transparent materials are needed for a range of applications. Here, we study the effect of crystallization on the mechanical and optical properties of barium titanosilicate glass-ceramics. We characterize the morphology and size of crystals to reveal the relationship between crystallinity, transparency, and mechanical properties. We find that the size and content of crystals increase upon heat-treatment of the precursor glass, which leads to an increase in fracture toughness (from 0.7 to 0.9 MPa m1/2) and hardness (from 5.8 to 6.6 GPa), reflecting that crystals hinder the propagation of cracks and that the glass-ceramics feature more bond constraints per unit volume, thereby improving the fracture toughness and hardness. There is a decrease in the crack initiation resistance. The transmittance decreases significantly upon crystallization due to light scattering. In conclusion, our study reveals a trade-off between fracture toughness and transparency in this series of glass-ceramics.