Strength and toughness of tape cast bioactive glass 45S5 following heat treatment

Tape cast and sintered (TCS) bioactive glass 45S5 has been shown to exhibit in vitro bioactivity in SBF and Tris, despite the formation of a crystalline phase (Na2Ca2Si3O9) during heat treatment. In this work, the effective porosity, hardness and flexural strength of TCS bioactive ceramic (composed of bioactive glass 45S5 prior to heat treatment) was determined as a function of the processing conditions (800, 900, and 1000 °C for 3 h and 1000 °C for 6 h). Additionally, the fracture toughness of the highest strength samples (1000 °C for 3 h, 1000(3)C, 83±13 MPa) was estimated by two independent methods: indentation strength and fractographic analysis. Hardness increased (0.2–5.7 GPa) with processing temperature and time, and this increase was inversely proportional to the decrease in effective porosity (1.14–0.02 cm3/g). The strength was also found to increase with temperature for samples heated for 3 h (30±4 to 83±13 MPa). The fracture toughness values obtained using the indentation strength method and fractographic analysis ranged from 0.9±0.2 to 1.1±0.2 MPam1/2. In addition, a higher porosity 1000(3)C type TCS bioactive glass-ceramic could also be fabricated without significantly decreasing the fracture toughness.