Process for the preparation of a voltage-dependent ceramic resistance based on ZnO, and a resistance produced by the process
US4767729A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 29, 1986 |
| Grant date | Aug 30, 1988 |
| Priority date | — |
| Expiry date | Apr 29, 2006 |
Classification
- Technology area (CPC H)Electricity
- CPC primaryH01C7/112
- WIPO fieldElectrical machinery, apparatus, energy
- WIPO sectorElectrical engineering
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 sil…
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.