Toughening of CaO-Al2O3-SiO2 glass by dmisteinbergite precipitation

Dmisteinbergite (CaAl2Si2O8), a metastable phase of anorthite, precipitated in CaO-Al2O3-SiO2 glass with MoO3 and carbon added as nucleating agents; dmisteinbergite precipitation was induced by a simple heat treatment at 1050 °C. Vickers indentation tests revealed substantial crack deflection as a result of the dmisteinbergite precipitation due to the high aspect ratio of its crystals and crystal fraction of ~30%. The stiffness of glass, as evaluated by Vickers indentation and bending tests, apparently decreased after heat treatment because of microcrack formation. After dmisteinbergite precipitation, the brittleness of glass, defined as toughness-to-hardness ratio, was ~30% of the original glass. Our results suggest a new approach for preparing a tough glass.