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:
Aug. 30, 1988
Filed:
Apr. 29, 1986
Maged A Osman, Zurich, CH;
Roger Perkins, Baden-Rutihof, CH;
Friedrich Schmuckle, Mellingen, CH;
Claus Schuler, Widen, CH;
BBC Brown, Boveri & Company, Limited, Baden, CH;
Abstract
A voltage-dependent ceramic resistance (varistor) based on ZnO and other addition elements, mostly in the form of oxides, is prepared, in that the addition elements are added to a suspension of ZnO powder in H.sub.2 O as chemical substances in the form of aqueous, mutually compatible, non-separating solutions of organic salts, acids, complex compounds and/or colloids, the suspension/aqueous solution formed in this manner is dried in the presence of air in a spray dryer, the free-flowing powder/granules prepared in this manner are pressed to a body and the pressed body is subjected to heat treatment, in order to decompose the organic substances, convert them into oxides, remove the decomposition products, and is finally sintered by successive heating to 650.degree. C., 900.degree. C. and 1100.degree. to 1300.degree. C. The water-soluble chemical substances to be used are preferably organic salts such as formates, acetates, lactates, tartrates, citrates, ammonium citrates and ammonium tartrates. Other suitable additions ar ammonia, ammonium salts of hydroxycarboxylic acids, organic amines, ammonium tetraborate, ammonium dichromate, ammonium silicotungstate, oligo-silicic acid and silicon hydroxide sol.