High Total Transmittance Alumina Discharge Vessels Having Submicron Grain Size

a technology of alumina discharge vessels and total transmittance, which is applied in the manufacture of electric discharge tubes/lamps, electrode systems, manufacturing tools, etc., can solve the problems of low total transmittance and relative population, and achieve the effect of increasing the total transmittance of co-doped alumina ceramics and low total transmittan

Inactive Publication Date: 2006-09-21
OSRAM SYLVANIA INC
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  • Description
  • Claims
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Benefits of technology

[0008] It is expected that additional co-doping of the PCA with ZrO2, Y2O3, Er2O3, Yb2O3, Sc2O3, etc., may alter the relative population of the point defects, but the problem of low total transmittance is expected to still exist because of the presence of MgO. Thus, the method of this invention should be useful to increase the total transmittance of such co-doped alumina ceramics.

Problems solved by technology

It is expected that additional co-doping of the PCA with ZrO2, Y2O3, Er2O3, Yb2O3, Sc2O3, etc., may alter the relative population of the point defects, but the problem of low total transmittance is expected to still exist because of the presence of MgO.

Method used

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  • High Total Transmittance Alumina Discharge Vessels Having Submicron Grain Size
  • High Total Transmittance Alumina Discharge Vessels Having Submicron Grain Size
  • High Total Transmittance Alumina Discharge Vessels Having Submicron Grain Size

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[0017] Both disks (˜25 mm diameter by 0.8 mm thick) and 70 W bulgy-shaped discharge vessels were made by sinter-HIPing. The starting submicron-grained alumina powder had a 150 nm mean particle size and was doped with 220 ppm MgO. For the disks, the measured in-line transmittance was typically quite uniform within the same disk, and from disk to disk. The as-made, sinter-HIPed bodies had very few residual pores. The average grain size was about 0.5 microns. Grain size was determined by multiplying a factor of 1.5 to the intercept size measured using images acquired via scanning electron microscopy (SEM).

[0018] The total transmittance values measured for the sinter-HIPed discharge vessels (polished or non-polished with a 0.8-mm wall thickness) were relatively low, ranging from 69-87% with an average of about 77%. The spectrophotometer in-line transmittance of polished 0.8 mm-thick disks at 600 nm was measured as 50-55%. After annealing at 1025-1150° C. in air for various durations (2...

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Abstract

The present invention uses a post-sinter-HIP anneal to increase the total transmittance of ceramic discharge vessels comprised of a submicron-grained alumina doped with MgO. After the anneal, the submicron-grained alumina discharge vessels have high values of both total and in-line transmittance, and are thus suitable for use in focused-beam, short-arc lamps. In particular, the total transmittance of the discharge vessel is increased to greater than 92% in the wavelength range from about 400 nm to about 700 nm.

Description

BACKGROUND OF THE INVENTION [0001] Translucent polycrystalline alumina (PCA) ceramic has made possible present-day high-pressure sodium (HPS) and ceramic metal halide lamps. The arc discharge vessels in these applications must be capable of withstanding the high temperatures and pressures generated in an operating lamp as well be resistant to chemical attack by the fill materials. In addition, the discharge vessels are typically required to have >92% total transmittance in the visible wavelength region from about 400 nm to about 700 nm in order to be useable in commercial lighting applications. [0002] In HPS lamps, the discharge vessels are tubular, whereas for ceramic metal-halide lamps discharge vessels can range from a cylindrical shape to an approximately spherical shape (bulgy). Examples of these types of arc discharge vessels are given in European Patent Application No. 0 587 238 A1 and U.S. Pat. No. 5,936,351, respectively. The bulgy shape with its hemispherical ends yield...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C04B35/115C04B35/64
CPCC04B35/115C04B35/6455C04B2235/3206C04B2235/5445C04B2235/652C04B2235/656C04B2235/6562C04B2235/6567C04B2235/658C04B2235/6582C04B2235/6584C04B2235/6588C04B2235/663C04B2235/664C04B2235/785C04B2235/9646C04B2235/9661H01J9/247H01J61/302
Inventor WEI, GEORGE C.
Owner OSRAM SYLVANIA INC
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