Ceramics-Silikáty 48, (3) 85 - 92 (2004)

The effect of hydrothermal treatment on the phase stability, microstructure and mechanical properties of tetragonal zirconia ceramics stabilized with 3 mol% yttria was studied. At temperatures of 140-260°C the tetragonal phase transformed into monoclinic zirconia. The degree of transformation increased with increasing temperature and time of ageing. Changes in the microstructure and mechanical properties were observed for the samples used at temperatures of 180°C and higher. The thickness of transformed layer increased with increasing temperature and at 260°C it reached a thickness of 170 µm after 10 hours. The changes in mechanical properties (hardness and fracture toughness) corresponded to the structural changes in the material caused by hydrothermal ageing. Temperatures of 180°C and higher were critical for the mechanical and structural properties of the material.