| Summary: | 碩士 === 國防大學中正理工學院 === 應用化學研究所 === 92 === The varistor precursor powders was fabricated by using the sol-gel method followed by calcination, ball milling, drying, pressing, sintering, electrode coating, and lead connecting to make a ZnO-based varistor. The more uniform and smaller particle size powders were made by sol-gel method. The experimental results showed that the stable gel was obtained during the precursor making step if the molar ratio of zinc nitrate to ethylene glycol was kept above 1:7. Furthermore, the mean particle size of the precursor powders was approximately 20nm after calcination of the gel. During the varistor preparation, the ZnO-based varistor with the better structure were obtained when the sintering temperature and the holding time was kept at 950℃ and one hour, respectively. The varistor through the sol-gel process has a high breakdown voltage 895V/mm and a nonlinear coefficient 58 compared to those through the conventional mixed oxide method.
Through the pulse wave tests, the largest breakdown voltage is 4kV in the response time of 20ns. The experimental results reveal that the ZnO-based varistors with a high breakdown field through a sol-gel method can be applied on the use of high current circuits and the surge suppressor for the electromagnetic pulse protection.
|
|---|
