The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 11, 2004
Filed:
Feb. 27, 2003
Osamu Asano, Hashima, JP;
NGK Insulators, Ltd., Nagoya, JP;
Abstract
The invention provides a method for producing a polycrystalline transparent sintered alumina body suitable for use in a ceramic envelope for a high intensity discharge lamp, with optimized kinds and amounts of sintering aids. First, adding and mixing, to alumina of a purity of 99.9% or higher, MgO within a range from 0.002 to 0.010 wt. % and La O within a range from 0.005 to 0.020 wt. %, in such a manner that a sum of MgO and La O is 0.030 wt. % or less and that a ratio thereof satisfies a relation 0.2≦MgO/La O ≦0.5. Next, firing a mixture at 900 to 1200° C. and cast molding the fired alumina. Then, after a chelating treatment, sintering the molded alumina for at least 1 hour at 1650 to 1900° C. in a reducing atmosphere under a normal pressure.