| 摘要 |
PROBLEM TO BE SOLVED: To obtain a member hardly corroded by gaseous halogen, etc., capable being sintered at relatively low temperature and useful in a light tube of a discharge lamp by using a light transmissive sintered compact having a garnet structure shown by a specific composition and having specific surface roughness, porosity and light transmissivity of visible rays. SOLUTION: The light transmissive member is the sintered compact having the garnet structure shown by the general formula Ln3Al5O12 (wherein Ln is at least one of Dy, Ho, Ym, Yb and Lu), below 1μm surface roughness (Ra), below 1% porosity and over 50% light transmissivity of visible rays. The crystal particle size hardly affects on corrosion resistance but affects on the mechanical strength necessary when the sintered compact is used as the member. When the crystal particle size is >=30μm, the mechanical strength is extremely lowered. Therefore the sintered compact having <=30μm crystal particle size is preferably used. This sintered compact is obtained by using powder having <=2μm average particle size as a starting material, compacting the starting material by a powder compacting method and a strip casting method and sintering the compact under a vacuum or gaseous hydrogen atmosphere.
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