| 摘要 |
PROBLEM TO BE SOLVED: To provide a sintered compact having a linear light transmittance of >=80% at a thickness of 1 mm in a wavelength range of 500 to 6μm. SOLUTION: A compact having a compact density of >=58% of a theoretical density ratio is produced by using high purity rare earth oxide raw material powder with a purity of >=99.9% containing Al in 5 to 100 wtppm expressed in terms of metal, and Si in <=10 wtppm expressed in terms of metal, and a binder. The binder is removed by heat treatment, and after that, the compact is sintered at 1,450 to 1,700 deg.C for >=0.5 hr in gaseous hydrogen, in a rare gas, or, in a vacuum, so that the light transmittable rare earth oxide sintered compact expressed by the general formula of R2 O3 (R is at least one kind of element selected from the group consisting of Y, Dy, Ho, Er, Tm, Yb and Lu) is obtained.
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