Effect of alumina on the strength, fracture toughness, and crystal structure of fluorcanasite glass-ceramics

The influence of alumina content (0-15 wt% Al2O3) on the indentation streng th, fracture toughness (K-Ic), and crystal structure of fluorcanasite (Al2O 3-CaO-F-K2O-Na2O-SiO2) glass-ceramics was analyzed. Increasing the Al2O3 co ntent from 0 wt% (CAN0) to 8 wt% (CAN8) caused the mean indentation strengt h and K-Ic values to decrease from 213 +/- 14 MPa and 2.7 +/- 0.1 MPa.m(1/2 ), respectively, for the CAN0 glass-ceramic to 78 +/- 16 MPa and 1.3 +/- 0. 2 MPa.m(1/2), respectively, for the CAN8 glass-ceramic. Increased Al2O3 con centrations (0-15 wt%) significantly affected the crystal size, crystal sha pe, aspect ratio, and crystal aggregation characteristics of the fluorcanas ite glass-ceramics. The addition of greater than or equal to 8 wt% of Al2O3 to fluorcanasite glass caused a transformation from canasite to leucite.