Transparent, infra-red transmitting glass-ceramics
AssigneeCorning Glass Works
InventorHermann L. Rittler
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Abstract
The instant invention relates to the production of highly-crystalline, transparent glass-ceramic articles wherein the predominant crystal phase is a beta-quartz solid solution and which demonstrate transmittances of infra-red radiations up to about 80% at a wavelength of 3.5 microns in bodies having thickness dimensions of about 4 mm. The articles of the invention have compositions within a very narrow area of the Li.sub.2 O--Al.sub.2 O.sub.3 --SiO.sub.2 field, nucleated with TiO.sub.2, and wherein some of the silica is replaced with AlPO.sub.4. Minor additions of ZrO.sub.2 enhance the chemical durability of the articles and, if desired, coloring agents can be added to yield colored, transparent, crystalline articles.
Claims1
A transparent glass-ceramic article exhibiting a coefficient of thermal expansion (R.T. to 300.degree. C.) less than about 10 .times. 10.sup..sup.-7 /.degree. C., excellent detergent durability, an infra-red transmittance at a wavelength of 3.5 microns through a polished plate of about 4 mm. thickness greater than 40%, and wherein the crystal phase consists essentially of beta-quartz solid solution, which consists essentially, by weight on the oxide basis, of about 3-4% Li.sub.2 O, 20-30% Al.sub.2 O.sub.3, 50-65% SiO.sub.2, 3-7% TiO.sub.2, 1.5-3% ZrO.sub.2, and 2-5% P.sub.2 O.sub.5, and wherein additional alkali metal oxides, the alkaline earth metal oxides, and B.sub.2 O.sub.3 are essentially absent.
Dependencies are inferred from the claim text.