Rapid sintering of 1.5 mol% yttria stabilized 3D-printed zirconia

The widely use of 3 mol% yttria stabilized zirconia (3YSZ) in technical applications is driven by the toughening effect provided by the tetragonal to monoclinic phase transformation during mechanical loading. Additive manufacturing has extended its use towards complex geometries, such as dental implants or heat exchangers, where reliability and durability are demanding. Recent studies have indicated enhanced damage tolerance when reducing yttria content in zirconia ceramics. However, conventional sintering of additively manufactured low-yttria stabilized zirconia causes crack formation due to spontaneous phase transformation during cooling down. In this work, a rapid sintering study of lithography-based additively manufactured 1.5YSZ ceramics is performed, aiming to fabricate crack-free complex shapes with retained tetragonal phase. A photosensitive slurry is developed for a 1.5YSZ powder in order to print, debind and rapid sinter prismatic bars for microstructural and phase analysis. A densification study is performed using a pressureless spark plasma sintering setup, varying heating rates (from 100 °C/min to 450 °C/min), dwell times (15 min to 30 min) and maximum temperatures (1200 °C to 1350 °C). Optimal conditions are found (sintering time of 30 min with a maximal temperature of 1200 °C) to densify fine-grained 1.5YSZ parts maintaining the tetragonal phase, which is demonstrated in a complex-shaped 3D-printed ceramic part.