Pressureless sintering behaviour of Al2O3/ZrO2 amorphous/solid solution powder with ultra-fine ZrO2 nanoparticle precipitation

In this paper, we present a novel Al2O3/ZrO2 amorphous/solid solution powder that exhibits a low pressureless sintering temperature and can precipitate numerous ultra-fine ZrO2 nanoparticles. The powder was prepared by combustion synthesis and bead milling. A series of characterizations were conducted to investigate the sintering behaviour and sintering activation energy of the as-synthesized powder. Commercial Al2O3 and ZrO2 powders with similar sizes were mixed and served as the referential sample. The experimental results and analysis indicated that the sintering activation energy and temperature of the Al2O3/ZrO2 amorphous/solid solution powder were much lower than that of the commercial powder due to its metastable state and lattice defects, its sintering activation energy and temperature were much lower than that of the commercial powder. As a result, its sintering temperature decreased to only 1400 degrees C, more than 100 degrees C lower than the commercial powder. Furthermore, we observed that the solid solution could decompose during sintering, forming a significant number of ultra-fine ZrO2 nanoparticles measuring 5 nm. These nanoparticles effectively enhanced the me-chanical performance of the ceramic by shifting the fracture mode from intergranular to transgranular. Conse-quently, the fracture toughness and bending strength of the ceramic could reach up to 6.03 MPa m0.5 and 525 MPa, respectively, which is much higher than that of the ceramic sintered with commercial powder. The insights gained from this study may be of assistance to the synthesis of high sintering activity ceramic powders and nanocomposite ceramics.