Incandescent lamp that emits infrared light and a method of making the lamp
View Patent ↗An incandescent lamp that emits infrared light and a method of making the lamp includes a filament assembly inside a polycrystalline aluminum oxide (PCA) envelope, where the filament assembly preferably has a coiled tungsten filament, solid metal ends of tungsten or molybdenum attached to the coiled tungsten filament, and leads at distal ends of the solid metal ends. End caps are attached to ends of the envelope and have openings through which a respective one of the leads extends, where the leads are each made of an electrically conductive material having a coefficient of thermal expansion compatible with the end caps, such as niobium. The leads are attached to the end caps with glass-ceramic sealing frits. The end caps and sealing frits seal a suitable gas inside the envelope.
1. An incandescent lamp that emits infrared light, comprising:
a filament assembly inside a tubular polycrystalline aluminum oxide envelope, said filament assembly having a coiled tungsten filament, solid metal ends of tungsten or molybdenum attached to distal ends of said coiled tungsten filament and first and second leads at respective distal ends of said solid metal ends;
polycrystalline aluminum oxide spacers disposed within the tubular envelope, each spacer having an opening through which the filament assembly passes, the coiled tungsten filament being stretched in regions where coiled tungsten filament passes through the spacers; end caps attached to ends of said envelope, wherein said end caps each have an opening through which a respective one of said first and second leads extends and wherein said first and second leads are each made of an electrically conductive material having a coefficient of thermal expansion compatible with said end caps; and
glass-ceramic sealing frits that attach each of said first and second leads to a respective one of said end caps, wherein said end caps and said sealing frits seal a gas inside said envelope.
2. The lamp of claim 1 , wherein said end caps comprise one of capillaries, recessed end buttons, and flanged end buttons.
3. The lamp of claim 1 , wherein the envelope contains a halogen-containing gas.
4. The lamp of claim 3 , wherein the halogen-containing gas is an iodine-containing or bromine-containing gas at a cold fill pressure of >1 atm.