Fabrication of Meta-Stable Monoclinic Zirconia Ceramics with a High Density Using a Piston-Cylinder Type High-Pressure Apparatus
Katsuya TAKAOKA, Ken HIROTA, Masaki KATO, Osamu YAMAGUCHI and Satoshi OHTAKA
Abstract:Single phase m-ZrO2 ceramics (`13 mm and 3-5 mmt) have been fabricated using a piston-cylinder type high-pressure apparatus under 1 Gpa at 1023-1173 K, in which a newly developed high-pressure cell has been utilized to introduce pseudo-isostatic pressure. Starting material, meta-stable m-ZrO2 powder prepared via a sol-gel method, was characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), and transmission electron microscopy (TEM). Dense ceramics sintered at 1123 K, free from macro-cracks, showed a high relative density of ~ 99.5% and homogeneous microstructures consisting of fine grains (`1m). In-situ XRD analysis under high pressures and temperatures revealed that m-to t-ZrO2 transition took place around 1123 K under 1 Gpa. Mechanical properties of m-ZrO2 ceramics have been evaluated; the maximum values of bending strength (b=520Mpa), Vickers hardness (Hv=9.8 Gpa), and fracture toughness (KIC=3.9 MpaEm1/2) were achieved at the samples fabricated at 1123 K. Key Words:High-pressure sintering, Zirconia (zirconium oxide), Pseudo-isostatic pressure, in-situ XRD analysis, Mechanical properties