Improved fracture toughness of ZrO2-Li2Si2O5 glass ceramics prepared by sol-gel method and spark plasma sintering

Although zirconia (ZrO 2 ) ceramics and lithium disilicate (Li 2 Si 2 O 5 ) glass ceramics are widely used in the field of dental restoration due to their superior properties, there remians an urgent demand to combine their complementary advantages through preparing composite materials for enhanced comprehensive performance to meet higher restoration requirements. In this study, ZrO 2 -Li 2 Si 2 O 5 powder was prepared through the sol-gel method and followed by spark plasma sintering at 900 °C for 10 min, the glass ceramics were successfully obtained. The effects of the ratio of ZrO 2 to Li 2 Si 2 O 5 on the phase composition, crystallinity, microstructure and mechanical properties of the glass ceramics were systematically investigated. The results showed that with the increase of Li 2 Si 2 O 5 content, the sintering densification process of glass ceramics was accelerated, and the crystallization of Li 2 Si 2 O 5 crystals gradually increased, while the content of t-ZrO 2 , m-ZrO 2 and ZrSiO 4 crystals decreased, and the grains size increased. Which led to an increase and then a decrease in mechanical properties, especially the fracture toughness. When ZrO 2 :Li 2 Si 2 O 5 is 1:2 (ZLS2), the glass ceramic exhibited the best comprehensive mechanical properties with a flexural strength of 390 ± 26 MPa and a significantly improved fracture toughness of 7.47 ± 0.42 MPa·m 1/2 . The improvement of performance is mainly due to the crack deflection, crack bridging, the stress caused by the differences in the coefficient of thermal expansion of different phases, and the dislocations generated in ZrO 2 .