The Densification and Microstructure of Y‐TZP Ceramics Formed Using the Hydrolysis‐Assisted Solidification Process

Abstract

Hydrolysis‐assisted solidification (HAS) was used in the slurry forming of yttria‐stabilized tetragonal zirconia (Y‐TZP) green bodies. AlN powder, a total of 1–5 wt% with respect to the solids, was added to a highly loaded aqueous zirconia (Y‐TZP) slurry containing 48.5 vol% of solids prior to shaping by aqueous injection molding. Aluminum hydroxide was formed during the hydrolysis of the AlN, which resulted in the production of dried green bodies with strength values ranging from 1.2 to 2.7 MPa. In the presence of alumina, formed by the thermal decomposition of the aluminum hydroxide in the green body, the densification and grain growth of the HAS‐formed material were enhanced. The fractional density, in the range 98.0–99.3%, and the bending strength, in the range 876–890 MPa, of a sintered Y‐TZP ceramic containing lower amounts (1 and 2.5 wt%) of AlN in the starting powder mixture did not differ significantly from the values obtained with conventionally formed reference material. The indentation toughness and Vickers hardness were both observed to increase, although this approximately 10% increase fell within a single standard deviation. The resistance to low‐temperature degradation of the HAS‐formed material, in terms of the thickness of the transformed monoclinic layer after aging for 24 h at 140°C in water, was found to be about four times lower and was statistically significant.