| 摘要 |
PROBLEM TO BE SOLVED: To obtain a light-transmissible material superior in corrosionproofness than silica glass and sapphire. SOLUTION: This material is a sintered compact consisting of polycrystalline rare earth element oxide and having a relative density of >=98.5% and having a linear transmittance of >=90% for the rays corresponding to visible to infrared region and material thickness of 5 mm, a transmittance loss of <=3%, and a corrosion resistance of <=2.0 nm/min in terms of corrosion rate by plasma irradiation. This material is obtained by the following process: rare earth element oxide powder >=99% in purity and <=5μm in average particle size is molded, the resulting molded form is fired at temperatures of 1,400-1,800 deg.C and then heat-treated at temperatures of 1,400-2,000 deg.C in the presence of a boron compound.
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