Additive-free preparation of high-toughness Al2O3/ZrO2 ceramics with platelet grain through spontaneously formed dendrite

Plate-like grain toughening is an effective approach to enhance the toughness of ceramics. Herein, we propose a novel method to prepare platelet-toughened Al2O3/ZrO2 ceramics by pressureless sintering without any additives. The Al2O3/ZrO2 powder was prepared through combustion synthesis assisted by rapid water cooling. The synthesis process involved ultra-high temperatures and a rapid cooling rate, leading to the formation of Al-Zr-Y oxide solid solution with gamma-Al2O3 or t-ZrO2 structure in the powders. The surface of the powder after being acid etched or annealed was investigated. The results indicated that the solid solution with gamma-Al2O3 structure exhibited a dendrite morphology, which could develop into plate-like Al2O3 grains during annealing or pressureless sintering. Platelets can effectively improve toughness by inducing crack deflection. Furthermore, numerous ZrO2 nanoparticles precipitated from the solid solution, which also contributed to the enhancement of mechanical properties. Consequently, the toughness and hardness of the ceramic could reach up to 10.76 MPa m(0.5) and 15.5 GPa, respectively. Additionally, this method could be applied to fabricate platelet-toughened Al2O3/ZrO2 ceramics with a wide range of Al2O3 contents (60 wt%similar to 80 wt%), thereby catering to a wide range of industrial applications.