Characteristics of Thermal Oxidation on Hot-Pressed Pure Yttria Ceramics

We investigated the characteristics of hot-pressed pure yttria ceramics, and annealed them in an oxidation atmosphere.Regardless of the heat treatment in the oxidation atmosphere, XRD analysis showed that all the samples had a Y 2 O 3 phase without structural change.Even though the color variation of the hot-pressed Y 2 O 3 ceramics was due to the sintering temperatures, the oxidation process turned the color of the Y 2 O 3 ceramics into white.The color change during oxidation treatment appears to be related to oxygen defects.In addition, oxygen defects also affected the weight change and microstructure of the Y 2 O 3 ceramics.The Y 2 O 3 ceramic sintered at 1600 o C had a 5.03 g/cm 3 density, which is close to the theoretical density of Y 2 O 3 .As the sintering temperature increased, small homogeneous grains grew to large grains which affected the Vickers hardness.Y 2 O 3 ceramics hot-pressed at 1600 o C and annealed at 1200 o C had a flexural strength of 140 MPa.