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:
Dec. 08, 1992
Filed:
Oct. 07, 1991
Applicant:
Inventors:
Kasuhiro Yamada, Kanagawa, JP;
Norifumi Yoshida, Fukui, JP;
Assignee:
Shin-Etsu Chemical Ltd., Tokyo, JP;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
C01F / ;
U.S. Cl.
CPC ...
423 211 ; 42324302 ; 423511 ; 4235762 ; 423210 ;
Abstract
An efficient method is proposed for decolorizing a rare earth oxysulfide, which is usually slightly colored in grey as prepared by the sulfiding reaction of a rare earth oxide with hydrogen sulfide, by removing sulfur impurity. The method comprises two steps of heat treatmentof which the first step is conducted in air at 450.degree. to 550.degree. C. for 2 to 5 hours and the second step is conducted in an inert gas, e.g., argon, at 800.degree. to 950.degree. C. for 2 to 5 hours.