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. 05, 1978
Filed:
May. 15, 1978
William R Manning, Richmond, MI (US);
Champion Spark Plug Company, Toledo, OH (US);
Abstract
A method for producing a dense and impervious stabilized hafnium oxide ceramic having zero percent water absorption is disclosed. The hafnium oxide is stabilized in the sense that a solid solution with Y.sub.2 O.sub.3 is formed. The solid solution has a cubic crystal structure which, because of its similarity to the structure of the mineral fluorite, is sometimes called a 'fluorite phase'; unlike hafnium oxide alone, which undergoes a destructive phase transformation from tetragonal to monoclinic during cooling, the cubic structure of the solid solution remains stable during cooling of a ceramic article. The ceramic is made by producing an intimate dry mixture consisting essentially, on an oxide basis, of hafnia, yttria and at least one oxide selected from the group consisting of silica, alumina, calcia, magnesia, baria and strontia, yttria constituting substantially 8 to 12 mole percent of said article based upon the total number of moles of hafnia and yttria, and silica, alumina, calcia, magnesia, baria and strontia constituting from 1/4 percent to 4 percent, based upon the weight of hafnia and yttria, with the proviso that calcia, magnesia, baria and strontia constitute not more than 70 percent by weight of the total of silica, alumina, calcia, magnesia, baria and strontia, pressing the dry mixture into a predetermined shape, and sintering the shape to a gas impervious condition at a temperature from 2700.degree. F. to 3000.degree. F. A stabilized, dense, hafnium oxide ceramic has the capability of conducting oxygen anions, a requisite of the solid electrolyte in an oxygen concentration cell. Such a cell can be used as an oxygen sensor in apparatus for controlling the operation of an internal combustion engine to maintain substantially the stoichiometric air-fuel ratio. When the air-fuel ratio is closely controlled, a three-way catalytic converter can be used to control emissions of hydrocarbons, CO and NO.sub.x within the limits presently specified for 1978.