Interface controlled active fracture modes in glass-ceramics

The active fracture modes in glass-ceramics, produced by controlled crystallization from three starting vitreous products containing PbO and SiO₂, were studied and compared. The goal was to examine the active fracture modes in PbO-rich glass-ceramic materials, where the main glass former was PbO, and compare these results with those reported in the literature, where the main glass former was SiO₂. The influence of composition, shape and mean size of the ceramic phase on the active fracture modes of the glass-ceramics was also examined. It was observed that the microhardness and fracture toughness of the starting vitreous products decrease with increasing PbO content. Increase in the relative amount of SiO₂ resulted in a decrease of the percentage of the ceramic phase. Glass-ceramics with higher PbO content showed typical behaviour of high toughness material, i.e. intergranular fracture mode, with lower microhardness value. Glass-ceramics with lower PbO content showed typical behaviour of high-strength material, i.e. transgranular fracture mode, with higher microhardness value.