| 摘要 |
PURPOSE:To obtain a zinc oxide varistor whose varistor voltage is low and whose voltage nonlinearity is high by adding a grain growth accelerator composed of MgO to a ZnO granulated powder having varistor characteristics. CONSTITUTION:Bi2O3, CoO, MnO2, Sb2O3, NiO, Cr2O3 and TiO2 in individually prescribed amounts are added to a ZnO powder; a binder and water are added to this mixture and are mixed, a slurry is produced, this slurry is dried by using a spray drier, this dried slurry is granulated and a basic material is obtained. Then, a binder and water are added to an MgO powder and are mixed, this mixture is dried by using the spray drier, this dried mixture is granulated, and a granulated powder is obtained as a grain growth accelerator. During this process, a drying condition is changed properly, and a grain growth accelerator whose average grain diameter is 10-50mum is obtained. This grain growth accelerator in a proper amount is added to the basic material, a raw material powder for a low-voltage varistor is produced, and this raw material powder is pressurized, molded and, after that, sintered. By this setup, a ZnO crystal is dispersed and arranged inside a sintered substrate, and an excellent voltage nonlinearity index can be obtained. |
