Microstructure and Phase Stability of Yttria‐Doped Tetragonal Zirconia Polycrystals Heat Treated in Nitrogen Atmosphere

Abstract

The low‐temperature degradation of zirconia (ZrO 2 ) that was doped with 3 mol% yttria (Y 2 O 3 ) (3Y‐TZP) was prevented by the heat treatment of sintered specimens in nitrogen. The heat treatment of sintered specimens resulted in a surface layer that was stabilized by nitrogen ions, whereas the interior was only slightly affected by the heat treatment. X‐ray diffractometry and transmission electron microscopy analyses revealed that the stabilized surface layer consisted of cubic grains with tetragonal precipitates. Although the presence of the surface layer decreased the strength of the sintered 3Y‐TZP, the strength of nitrified specimens was maintained when low‐temperature annealing was applied.