Y

1. A corrosion resistant member comprising a Y 2 O 3 sintered material that includes 99.9% by weight or more Y in terms of Y 2 O 3 , wherein

said Y 2 O 3 sintered material comprises at least metal element of AE, wherein AE is a group II element of the periodic table, and

wherein a difference in crystal grain size between the surface and the inside region of said Y 2 O 3 sintered material is not larger than 30 μm.

2. The corrosion resistant member according to claim 1 , wherein said Y 2 O 3 sintered material further comprises any one of Si, Fe and Al.

3. The corrosion resistant member according to claim 1 , wherein said Y 2 O 3 sintered material comprises a non zero amount of Si, Fe, Al and AE (these metallic elements will hereinafter be collectively referred to as metal elements M), in concentrations of 300 ppm of less for Si in terms of SiO 2 , 50 ppm or less for Fe in terms of Fe 2 O 3 , 100 ppm or less Al in terms of Al 2 O 3 and 350 ppm or less AE, wherein AE is a group II element of the periodic table, in terms of AEO, wherein AEO is a compound containing the AE and O.

4. The corrosion resistant member according to claim 3 , wherein the content ratio of any of the metal elements M contained at and near the surface to that contained deep inside of said Y 2 O 3 sintered material is in a range from 0.2 to 5.

5. The corrosion resistant member according to claim 1 , wherein said Y 2 O 3 sintered material shows dielectric loss tangent of 2×10 −3 or less in a frequency range from 10 MHz to 5 GHz.

6. The corrosion resistant member according to claim 1 , having a carbon content in said Y 2 O 3 sintered material that is 100 ppm by weight or less.

7. The corrosion resistant member according to claim 1 , wherein said Y 2 O 3 sintered material has void ratio of 5% or less.

8. The corrosion resistant member according to claim 1 , wherein said Y 2 O 3 sintered material has density of 4.8 g/cm 3 or higher.