Preparation of alumina-toughened zirconia via 3D printing and liquid precursor infiltration: manipulation of the microstructure, the mechanical properties and the low temperature aging behavior

In this study, we propose an integrated approach which combines 3D printing and liquid precursor infiltration together to prepare alumina-toughened zirconia (ATZ) composite. Controllable manipulation of the microstructure of the composite could be realized through different infiltration times and sintering temperature. The 3D-printed ATZ with infiltration and post-CIP sintered at 1550 °C possesses the highest relative density (98.11%), hardness (12.65 ± 0.24 GPa) and fracture toughness (6.42 ± 0.33 MPa m^1/2). The rates of increase in the performance compared with the undoped zirconia sintered at 1550 °C are 1.8%, 8.4% and 34.6%, respectively. The dominated toughening mechanism of ATZ could be attributed to the effect of Al₂O₃ inclusion on crack deflection and energy absorption. The 3D-printed ATZ sample with infiltration followed by CIP sintered at 1550 °C shows the lowest aging rate and the lowest phase transformation depth compared with 3Y-TZP (Tetragonal Zirconia Polycrystal). Our integrated approach could not only realize the complex and ultrafine shape free of molds, but also suppress the low temperature aging behavior of dental implants, which has baffled dentists for a long time.