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US 4,057,434 AGranted
Opaque infra-red transmitting glass-ceramic articles
AssigneeCorning Glass Works
InventorHermann L. Rittler
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AssigneeCorning Glass Works
InventorHermann L. Rittler
Estimating the term…
This invention relates to the manufacture of highly-crystalline, opaque glass-ceramic articles, wherein the primary crystal phase is a beta-spodumene solid solution, which exhibit coefficients of thermal expansion (25.degree.-700.degree. C.) less than about 15 .times. 10.sup.-7 /.degree. C. and, preferably, less than 10 .times. 10.sup.-7 /.degree. C., and wherein transmittances to infra-red radiations as great as 60% have been measured at a wavelength of 3.5 microns in samples having thicknesses of about 4.25 mm. Such articles have compositions circumscribed within a narrow field of the Li.sub.2 O--Al.sub.2 O.sub.3 --SiO.sub.2 system nucleated with TiO.sub.2 which contain ZnO as the principal modifier ion and are essentially free from the alkaline earth metal oxides, alkali metal oxides other than Li.sub.2 O, and ZrO.sub.2.
An opaque glass-ceramic article demonstrating a coefficient of thermal expansion (20.degree.-700.degree. C.) less than 15, excellent chemical durability, an infra-red transmittance at a wavelength of 3.5 microns through a polished plate of about 4.25 mm. thickness in excess of 40%, and wherein beta-spodumene solid solution constitutes the principal crystal phase, consisting essentially, by weight on the oxide basis, of about 2.5-4.5% Li.sub.2 O, 0.75-3.5% ZnO, 17.5-21% Al.sub.2 O.sub.3, 65-71% SiO.sub.2, 3.5-6% TiO.sub.2, and being essentially free from alkaline earth metal oxides, alkali metal oxides other than Li.sub.2 O, and ZrO.sub.2.
Dependencies are inferred from the claim text.