| 摘要 |
PURPOSE:To obtain a high-strength calcined compact of zirconia improved in bending strength, by hydrothermally treating a calcined compact of zirconia containing tetragonal zirconia as a constituent crystal phase at a specific temperature. CONSTITUTION:A calcined compact of zirconia containing tetragonal zirconia as a main constituent crystal phase is hydrothermally treated at 60-300 deg.C to subject the surface of the calcined compact to crystal phase transfer from tetragonal zirconia to monoclinic zirconia. Thereby, the aimed calcined compact is obtained. The treating time may be relatively short in the case of about 200 deg.C treating temperature. The treating time must be prolonged with increasing difference between 200 deg.C and the treating temperature. The phase transition is hardly advanced at <60 deg.C and apparatus cost is increased at >300 deg.C. Thereby, the high temperature is industrially unsuitable. Methods for dipping the calcined compact in water and simply bringing steam into contact with the surface of the calcined compact are convenient and preferred for the hydrothermal treatment. The hydrothermal treatment is preferably carried out after precise machining the surface of the calcined compact. |
