| 摘要 |
PURPOSE:To obtain the titled composition which is little in the difference of thermal expansion coefficient for alumina and excellent in resistance to halogen vapor and suitable for sealing of the end part of a discharge lamp, by incorporating Al2O3, SiO2, Eu2O3 and oxide selected from among Sc2O3, Yb2O3, Tm2O3, TiO2 and ZrO2 in the specified proportion. CONSTITUTION:Composition for sealing is constituted of (A) 8-30wt.% aluminum oxide, (B) 12-40wt.% silicon dioxide, (C) 30-60wt.% europium oxide and (D) <=15wt.% at least one kind selected from among scandium oxide, ytterbium oxide, thullium oxide, titanium oxide and zirconium oxide. Since this composition for sealing is good in wettability for material such as alumina ceramics used as a luminous tube of a metallic halide lamp or the like and has slight difference of thermal expansion coefficient for these materials, generation of a crack resulting from thermal stress or the like is little.
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