Study On The Low Temperature Sintering And Tape-Casting Of ZnO Varistor Ceramics

Nowadays ZnO varistor's ceramic tape can't be sintered with inner electrode below 1000℃, so Pd and Pd/Ag must be chosen as MLCV's inner electrode, that have higher sintering temperature but more expensive than pure Ag. This is why the cost of MLCV is too high. To solve the problem above, low temperature sintering of ZnO varistor ceramics and tape-casting of ZnO varistor ceramic tape were studied in this paper. The conclusions are as following:The organic additives'mechanism, selective rules and their roles in preparing tape-casting ceramic slurry were discussed. The organic additives included dispersant, binder, plasticizer and solvent. Based on the characteristic of ZnO varistor's green powder, castor oil was chosen as dispersant, PVB was chosen as binder, DBP was chosen as plasticizer, and n-butanol with cyclohexanone were chosen as dual-combining solvent. The mechanism and the methods of low temperature sintering ZnO varistor ceramics were investigated. After summarizing several designs for low temperature sintering ZnO varistor ceramics, an optimal recipe for low temperature sintering ZnO-Bi varistor ceramics was presented. To prove the property of the recipe, some ZnO varistor specimens were made by traditional dried mould process using the optimal recipe mentioned above. And the experimental results showed that, the sintering temperature of the specimens could be as low as 950℃.The experiment of preparing ZnO varistor's green tape using tape-casting technique had been done. And the influence of organic additives'different adding amount on the property of ceramic slurry and the ZnO varistor's green tape were studied systematically. Finally the best adding amount of the organic additives including dispersant, binder, plasticizer and solvent were determined.The organic burnout process and the sintering process of green tape prepared by tape-casting were discussed. The experimental results showed that, the ZnO varistor's green tape could successfully be sintered at 950℃. This tape could be used for manufacturing MLCV.