Monolithic seal for a sapphire metal halide lamp
A ceramic metal halide discharge lamp may be made having a monolithic seal between a sapphire arc tube and a polycrystalline alumina cap. The lamp is made by providing an arc tube of fully dense sapphire and providing a cap made of unsintered compressed polycrystalline alumina doped with magnesium oxide and yttrium oxide. The cap is presintered to remove binder material at a low temperature. The presintered cap is placed on an end of the arc tube to form a close interface. The presintered cap and arc tube are then heated to until the cap is fully sintered onto the arc tube and the sapphire tube grows into the cap. A monolithic seal is formed along the interface as the sapphire grows into the polycrystalline alumina.
Osram Sylvania Inc.
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George C. Helmar G. Arlene Dieter
Wei Adler Hecker Lang