Abstract: The instant invention is directed to the production of glass-ceramic articles from thermally crystallizable glass compositions containing, by weight, about 40-85% SiO.sub.2 and 2.5-17% N as basic constituents and utilizing such modifiers as the alkali metals, the elements of Groups IIA and IIB of the Periodic Table, boron, and aluminum to obtain practical glass-forming compositions. In general, at N contents greater than about 3.5%, the predominant crystal phase developed in situ will customarily comprise "nitrogen mullite", silicon oxynitride (Si.sub.2 ON.sub.2), and/or .beta.'-Si.sub.3 N.sub.4 solid solution. The crystal phase which has been denominated in the literature as "nitrogen-mullite" has a lath-like morphology and, hence, is useful in reinforcing the crystalline body. Where the predominant crystal phase comprises a silicate, it is believed that nitrogen is present in some manner within the silicate crystal structure. The parent thermally crystallizable glasses appear to be self-nucleating, i.e.

Abstract: A method of forming graded index, nitrogen-doped optical waveguides. A cylindrically-shaped porous preform comprising at least two oxides is initially formed. One of the oxides, which more readily reacts with nitrogen, has a greater concentration near the center of the preform than at the outer portion thereof. The preform is treated with a nitrogen-containing compound to form a porous body having a greater concentration of nitrogen in the central portion thereof. The porous preform is consolidated and drawn into an optical waveguide filament.

Abstract: The instant invention is directed to the production of glass-ceramic articles from thermally crystallizable glass compositions containing, by weight, about 40-85% SiO.sub.2 and 2.5-17% N as basic constituents and utilizing such modifiers as the alkali metals, the elements of Groups IIA and IIB of the Periodic Table, boron, and aluminum to obtain practical glass-forming compositions. In general, at N contents greater than about 3.5%, the predominant crystal phase developed in situ will customarily comprise "nitrogen mullite", silicon oxynitride (Si.sub.2 ON.sub.2), and/or .beta.'-Si.sub.3 N.sub.4 solid solution. The crystal phase which has been denominated in the literature as "nitrogen-mullite" has a lath-like morphology and, hence, is useful in reinforcing the crystalline body. Where the predominant crystal phase comprises a silicate, it is believed that nitrogen is present in some manner within the silicate crystal structure. The parent thermally crystallizable glasses appear to be self-nucleating, i.e.

Abstract: The instant invention is directed to the production of glass-ceramic articles from thermally crystallizable glass compositions containing, by weight, about 40-85% SiO.sub.2 and 2.5-17% N as basic constituents and utilizing such modifiers as the alkali metals, the elements of Groups IIA and IIB of the Periodic Table, boron, and aluminum to obtain practical glass-forming compositions. In general, at N contents greater than about 3.5%, the predominant crystal phase developed in situ will customarily comprise "nitrogen mullite", silicon oxynitride (Si.sub.2 ON.sub.2), and/or .beta.'--Si.sub.3 N.sub.4 solid solution. The crystal phase which has been denominated in the literature as "nitrogen-mullite" has a lath-like morphology and, hence, is useful in reinforcing the crystalline body. Where the predominant crystal phase comprises a silicate, it is believed that nitrogen is present in some manner within the silicate crystal structure. The parent thermally crystallizable glasses appear to be self-nucleating, i.e.

Abstract: The instant invention is directed to the production of glass-ceramic articles from thermally crystallizable glass compositions containing, by weight, about 40-85% SiO.sub.2 and 2.5-17% N as basic constituents and utilizing such modifiers as the alkali metals, the elements of Groups IIA and IIB of the Periodic Table, boron, and aluminum to obtain practical glass-forming compositions. In general, at N contents greater than about 3.5%, the predominant crystal phase developed in situ will customarily comprise "nitrogen mullite," silicon oxynitride (Si.sub.2 ON.sub.2), and/or .beta.'-Si.sub.3 N.sub.4 solid solution. The crystal phase which has been denominated in the literature as "nitrogen-mullite" has a lath-like morphology and, hence, is useful in reinforcing the crystalline body. Where the predominant crystal phase comprises a silicate, it is believed that nitrogen is present in some manner within the silicate crystal structure. The parent thermally crystallizable glasses appear to be self-nucleating, i.e.

Abstract: The instant invention is directed to the production of glass-ceramic articles from thermally crystallizable glass compositions containing, by weight, about 40-85% SiO.sub.2 and 2.5-17% N as basic constituents and utilizing such modifiers as the alkali metals, the elements of Groups IIA and IIB of the Periodic Table, boron, and aluminum to obtain practical glass-forming compositions. In general, at N contents greater than about 3.5%, the predominant crystal phase developed in situ will customarily comprise "nitrogen mullite", silicon oxynitride (Si.sub.2 ON.sub.2), and/or .beta.'-Si.sub.3 N.sub.4 solid solution. The crystal phase which has been denominated in the literature as "nitrogen-mullite" has a lath-like morphology and, hence, is useful in reinforcing the crystalline body. Where the predominant crystal phase comprises a silicate, it is believed that nitrogen is present in some manner within the silicate crystal structure. The parent thermally crystallizable glasses appear to be self-nucleating, i.e.