| 摘要 |
1,147,847. High refractive index glass compositions. BENDIX CORP. 12 Jan., 1968 [20 Jan., 1967], No. 1967/68. Heading C1M. A glass composition having a refractive index of at least 1À83 comprises from 5 to 20% by weight of Nb 2 O 5 ; from 0 to 10% by weight of Ta 2 O 5 , the amount of Ta 2 O 5 not exceeding 50% by weight of the amount of Nb 2 O 5 ; from 15 to 45% by weight of BaO; from 15 to 30% by weight of La 2 O 3 ; from 5 to 20% by weight of TiO 2 , and from 15 to 30% by weight of silica up to 60% by weight of which may be substituted by boric oxide. Other alkaline earth metal oxides such as calcium oxide and strontium oxide may be added in amounts up to 10% by weight. Zinc or cadmium oxide or a mixture thereof may be included in amounts up to 15% by weight and the presence of alkali metal oxides such as sodium, potassium or lithium oxides is useful in amounts up to 5% by weight in controlling thermal expansion and softening point. The glass compositions may be prepared by melting a mix of the batch components in conventional crucibles, e.g. platinum crucibles. Nb, La, Ta, Zn, Cd are added as oxides. Ba may be added as oxide, carbonate or peroxide. Ca, Sr, Na, K, Li may be added as carbonates. Silica may be added as high grade quartz sand and boron as boric acid. The glasses melt and refine at temperatures between 2450‹ and 2600‹ F. and can be reheated and drawn into rods or fibres at 1500‹ F. or less. The glasses are virtually colourless and make excellent optical glasses and can be used in AbbÚ type refractometers for the prisms, and can be used as core glass in fibre-optic structures.
|
