Ceramic discharge vessel with chromium-coated niobium feedthrough and discharge lamp containing same
AssigneeOsram Sylvania Inc.
InventorsGeorge C. Wei, Domenic Checca
Life of this patent
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Abstract
There is described a lamp having a ceramic discharge vessel with a niobium feedthrough that has been coated with a layer of chromium to provide oxidation resistance. In a preferred method, a slurry containing chromium powder is applied to the niobium feedthrough and dried. A sub-assembly is formed by inserting the coated niobium feedthrough into an annular polycrystalline alumina (PCA) disc and heated in vacuum to 1700° C. to 1900° C. to bond the feedthrough to the PCA and form the sub-assembly and an oxidation-resistant coating on the feedthrough. The sub-assembly is then sealed to a ceramic body of the discharge vessel in a conventional manner.
Claims8
A discharge lamp comprising:
- a ceramic body formed of polycrystalline alumina;
- the ceramic body having at least one seal and enclosing a discharge space, the discharge space containing a discharge sustaining medium and at least one electrode;
- and
- the at least one seal having a niobium feedthrough sealed therein for making an electrical connection between the at least one electrode and an external power source, the niobium feedthrough having a layer consisting of chromium or an alloy of chromium and niobium on an external surface to provide oxidation resistance.
A discharge lamp comprising:
- a tubular body formed of polycrystalline alumina;
- a pair of seals, each sealing an end of said body;
- and
- said seals each comprising an annular polycrystalline alumina disc, the outer surface of said disc being bonded to said body, and a tubular niobium feedthrough sealed to the inner surface of said disc in a seal area, the niobium feedthrough having a layer consisting of chromium or an alloy of chromium and niobium on an external surface, the layer in the seal area being between the feedthrough and the disc.
A method of making a ceramic discharge vessel, comprising:
- forming a tubular polycrystalline body;
- forming a pair of annular polycrystalline alumina sealing discs;
- forming a pair of niobium feedthroughs, each of said feedthroughs having an area for sealing to said discs;
- providing coating an external surface of the niobium feedthroughs with a layer consisting of chromium;
- inserting said each of said feedthroughs into one of said discs to form sub-assemblies;
- firing said sub-assemblies in a vacuum at 1700° C. to 1900° C. to seal the discs to the respective sealing area;
- and
- subsequently inserting said fired sub-assemblies into opposite ends of said tubular body and sealing thereto.
A feedthrough for a ceramic discharge vessel, the feedthrough comprising a niobium tube having a layer consisting of chromium or an alloy of chromium and niobium on an external surface to provide oxidation resistance.
Dependencies are inferred from the claim text.