| 摘要 |
PROBLEM TO BE SOLVED: To obtain a lead-free heavy crown or especially heavy crown optical glass having a refractive index nd of 1.60-1.65, an Abbe's numberνd of 50-60, satisfactory meltability and workability, sufficient chemical resistance and high crystallization stability. SOLUTION: This glass has a compsn. consisting of, by weight on the oxide basis, 20-37% SiO2 , 8-20% B2 O3 , 43-55% BaO, 0.01-10% ZnO, 0-7% CaO, 0-7% MgO (CaO+MgO<=7% and BaO+ZnO+CaO+MgO<60%), 0.01-5% TiO2 , 0.01-7% ZrO2 , 0.1-10% Al2 O3 , 0-8% Na2 O, 0-8% K2 O (Na2 O+K2 O<=8%), 0 to <3% La2 O3 , 0-1% F<-> and 0-3% P2 O5 .
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