High total transmittance alumina discharge vessels having submicron grain size
View Patent ↗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.
1. A method of making a ceramic discharge vessel comprising:
(a) forming the discharge vessel with a submicron-grained alumina powder doped with MgO, the discharge vessel having a wall having a thickness of about 0.8 mm;
(b) sinter-HIPing the discharge vessel; and
(c) annealing the discharge vessel in an annealing atmosphere containing a partial pressure of oxygen of about 1×10 −3 atm to about 1×10 −9 atm to increase the total transmittance of the discharge vessel to >92% in a wavelength range from about 400 nm to about 700 nm.
2. The method of claim 1 wherein the discharge vessel is annealed at about 1000° C. to about 1150° C.
3. The method of claim 2 where the discharge vessel is annealed for about 1 hour to about 20 hours.
4. The method of claim 1 wherein the discharge vessel is annealed at about 1100° C. for about 2 hours.
5. The method of claim 1 wherein the partial pressure of oxygen is about 1×10 −5 atm to about 1×10 −7 atm.
6. The method of claim 5 wherein the discharge vessel is annealed at about 1000° C. to about 1150° C.
7. The method of claim 6 where the discharge vessel is annealed for about 1 hour to about 20 hours.
8. The method of claim 7 wherein the discharge vessel is formed with a submicron-grained alumina powder doped with about 200 ppm to about 800 ppm MgO.
9. The method of claim 8 wherein the annealing atmosphere is comprised of nitrogen or argon.
10. The method of claim 1 wherein the discharge vessel is formed with a submicron-grained alumina powder doped with about 200 ppm to about 800 ppm MgO.
11. The method of claim 10 wherein the submicron-grained alumina powder has a mean particle size of about 150 nm.
12. The method of claim 1 wherein the annealing atmosphere is comprised of nitrogen or argon.