Defects in the grain interiors of 3 mol% yttria-stabilized tetragonal zirconia polycrystal ceramics with 0.25 wt% alumina

The presence of high-density defects is rarely observed in the bulk 3 mol% yttria-stabilized tetragonal zirconia polycrystal (3Y-TZP) ceramics obtained through the conventional pressureless sintering routine. In the present work, the fine-grained dense 3Y-TZP ceramic of 147 nm was prepared by pressureless sintering a commercial 0.25 wt% alumina-doped zirconia powder at 1300 °C. A novel discovery was reported that large amounts of defects were present in the grain interiors of the sample. The phenomenon was further examined using three types of powder samples and the reasons for defect formation were investigated by microstructural characterizations using high-resolution transmission electron microscope (HRTEM) analysis and Rietveld refinement. The results confirmed the essential dependence of the defect formation on the alumina addition. The authors ascribed the defect formation to be resulted from the significant difference in ionic radii of the solvent and solute during the dissolution of alumina into zirconia lattice. The sintering kinetics was proposed to be enhanced with the presence of substantial defects, by which consequently favored the low-temperature sintering of the alumina-doped zirconia ceramics.