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US4767729A Process for the preparation of a voltage-dependent ceramic resistance based on ZnO, and a resistance produced by the process 失效
用于制备基于ZnO的电压依赖性陶瓷电阻的方法,以及由该方法产生的电阻

Process for the preparation of a voltage-dependent ceramic resistance
based on ZnO, and a resistance produced by the process
摘要:
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.
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