FABRICATION, MICROSTRUCTURAL CHARACTERIZATION, AND MECHANICAL-PROPERTIES OF POLYCRYSTALLINE T'-ZIRCONIA

Large-grained (100- to 200-mu-m), yttria-doped, polycrystalline t'-zirconia ceramics were fabricated by heat-treating presintered samples at temperatures greater-than-or-equal-to 2100-degrees-C. Polarized light microscopy revealed the ferroelastic domain structure in the t' samples. XRD showed that no monoclinic phase was detected on as-polished, ground and fracture surfaces, or on surfaces while under a tensile stress as high as 400 MPa. By contrast, relative changes occurred in the tetragonal peak intensities, which were attributed to ferroelastic domain switching. The higher toughness of 3-mol%-Y2O3-doped t' samples (7.7 MPa.m-1/2) compared to that of 8 mol% Y2O3 cubic samples (2.4 MPa.m-1/2) was explained in part by ferroelastic domain switching.