Sealing composition for sealing aluminum nitride and aluminum oxynitride ceramics
a technology of aluminum oxynitride and composition, which is applied in the manufacture of cold cathode, electrode system, electric discharge tube/lamp, etc., can solve the problems of limiting the durability and life of short-arc lamps such as projection lamps and automotive headlights, and pca discharge vessels are generally not suitable for focused beams, etc., to reduce or eliminate the formation of frit seals
Inactive Publication Date: 2010-06-03
OSRAM SYLVANIA INC
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Benefits of technology
[0011]It is another object of the invention to provide a sealing composition for sealing aluminum nitride and aluminum oxynitride ceramics that reduces or eliminates bubble formation in frit seals.
Problems solved by technology
Yet despite its pervasive use, PCA is not used in some HID applications because it is only translucent and not transparent.
In particular, a PCA discharge vessel is generally not suitable for focused-beam, short-arc lamps such as projection lamps and automotive headlights.
In addition, PCA discharge vessels although superior to quartz arc tubes in metal halide lamps can react with the rare earth halide fills limiting the durability and life of such lamps.
Despite the potential advantages of aluminum nitride and aluminum oxynitride ceramics, there remain a number of technical difficulties which must be overcome for these materials to be considered for use in HID lamp applications.
Since most of the nitrogen evolved from the reaction cannot be accommodated in the molten frit, it escapes as gas bubbles into the frit seal.
These gas bubbles may degrade the quality and function of the hermetic seal leading to premature failure of the lamp, particularly when higher pressures are present in the discharge vessel.
Method used
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[0028]FIG. 2 is a cross-sectional photomicrograph of an aluminum nitride capillary that has been sealed with a frit consisting of 20 wt. % Al2O3, 15 wt. % SiO2 and 65 wt. % Dy2O3 (20Al2O3—15SiO2—65Dy2O3). The presence of gas bubbles in the seal is readily apparent.
[0029]FIG. 3 is a cross-sectional photomicrograph of a similar aluminum nitride capillary sealed with the same 20Al2O3—15SiO2—65Dy2O3 frit used in FIG. 1 except that 5 wt. % Si has been added based on the weight of the oxide mixture. In this case, there are no discernible gas bubbles in the frit which indicates that the addition of Si has suppressed the release of nitrogen during the sealing process.
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Abstract
There is described a sealing composition for sealing aluminum nitride and aluminum oxynitride ceramics comprising: a mixture of SiO2, at least one other metal oxide, and a silicon additive comprising at least one of silicon metal or a silicide. The silicon additive acts to suppress the formation of nitrogen bubbles during the sealing of articles comprised of aluminum nitride or aluminum oxynitride ceramics, e.g., as in the case of a ceramic discharge vessel for a high intensity discharge lamp.
Description
TECHNICAL FIELD[0001]The present invention relates to aluminum nitride and aluminum oxynitride ceramics and in particular to the use of such ceramics for arc discharge vessels in high-intensity discharge (HID) lamps, e.g., metal halide lamps and high-pressure sodium lamps (HPS).BACKGROUND OF THE INVENTION[0002]Metal halide and high-pressure sodium lamps are two examples of lamps which use a discharge vessel made of a ceramic material. The robustness of the ceramic material permits the use of more corrosive chemical fills and allows the discharge vessels to be operated at higher temperatures. A sealing composition, commonly referred to as a frit, is used to form a hermetic seal between the feedthrough sections of the electrodes and the ceramic body of the discharge vessel. The sealing composition may also be used to join together the ceramic pieces which form the discharge vessel.[0003]FIG. 1 shows a discharge vessel 1 for a conventional ceramic metal halide lamp. The discharge vesse...
Claims
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IPC IPC(8): H01J61/30
CPCC03C8/24C04B37/005C04B2237/095C04B41/5022C04B41/009C04B41/86H01J9/266C04B2237/062C04B2237/066C04B2237/10C04B2237/366C04B35/581C04B41/5096C04B41/5071
Inventor ZHENG, YIMARLOR, RICHARD C.WEI, GEORGE C.
Owner OSRAM SYLVANIA INC