Patent ID: 7435698

Claim:
A rare-earth oxide sintered body comprising at least one of La 2 O 3 , Nd 2 O 3 , Sm 2 O 3 , Eu 2 O 3 , Gd 2 O 3 , Dy 2 O 3 , Ho 2 O 3 , Er 2 O 3 , Tm 2 O 3 , Yb 2 O 3 , Lu 2 O 3 , and Sc 2 O 3 , and at least one of Ln 3 BO 6 (Ln=La, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, and Lu), and Sc 3 BO 6 as a main constituent crystal thereof, wherein the sintered body is formed using a boron compound at a ratio of 0.06 mol % or more and less than 25 mol % when converted into boron oxide (B 2 O 3 ) to an oxide powder of at least one of Ln and Sc.