Sol-gel preparation of ZrO₂-Li₂Si₂O₅ ceramics and their sintering properties

Despite zirconia (ZrO₂) ceramics and lithium disilicate (Li₂Si₂O₅) glass-ceramics have been widely applied on the market for dental restorations, composites that can combine the advantages of both are still demanded. Here we introduced a ZrO₂-Li₂Si₂O₅ ceramic with minimized glass phases that fabricated through a sol-gel method and subsequent pressureless sintering. ZrO₂-Li₂Si₂O₅ powders were obtained after the gel precursors were heat treated under 800 °C. The gel-derived powders were molded and pressureless sintered under 900-1000 °C to investigate their sintering properties. From the microstructures of the sintered samples, we knew that the densification process was dominated by the growth of Li₂Si₂O₅ grains instead of the growth of ZrO₂ grains. Increasing in Li₂Si₂O₅ content can promote ceramic densification. Interestingly, reactions between ZrO₂ and Li₂Si₂O₅ were observed with sintering temperature higher than 916 °C, which can increase the porosity of the ceramics. Therefore, both the content of Li₂Si₂O₅ and sintering temperature should be well adjusted to achieve samples with desired properties. Finally, ceramics with flexural strength of 226 MPa and porosity of 0.4% were achieved from powders with moderate Li₂Si₂O₅ content after sintering at 1000 °C.