| 摘要 |
PURPOSE:To improve a discharge withstand current rating, and to reduce the dispersion of characteristics by preforming a granular material at pressure of 100MPa or less through compression molding, degreasing and treating an organic component, cold isotropic-compressing treating the material at pressure of 200MPa or more and baking the treated material. CONSTITUTION:A zinc oxide raw material adjusted in specified grain size and a fixed quantity of an additive composed of BiO2O3, Co3O4, etc., are mixed. A fixed quantity of polyvinyl alcohol aqueous solution, etc., are added to these raw material powder, and a granular material is acquired, and molded in a predetermined shape under preforming pressure of 8-100MPa by a hydraulic molding press. The molded material is degreased under the conditions of degreasing treatment of 500 deg.CX5hr, and the cold isotropic compression treatment of molding pressure of 200-680MPa is executed, thus manufacturing a degreased body. The side face of the degreased body is coated with mixed paste for a side-face high resistance layer in thickness of 60-300mum, and the degreased body is baked permanently under the conditions of a temperature elevating rate of 40-60 deg.C/hr preferably 1100-1250 deg.C/3-7hr. Accordingly, lighting surge resistance is increased, and the dispersion of characteristics is reduced while a voltage nonlinear resistor, internal defects of which are decreased, can be acquired. |
