| 摘要 |
PURPOSE:To reduce the shrinkage distortion of the outer surface of a material at the time of sintering and to obtain a varistor having excellent surge resistance by forming the outer surface of a varistor material of high formation density layer. CONSTITUTION:A disclike varistor material 3 is composed by incorporating, for example, zinc oxide as a main ingredient, employing ceramic powder suitably added with metal oxide to the zinc oxide to provide notches 1 of oblique outer peripheral edges at both front and rear faces, and forming the outer surfaces of the notches 1 in thicknesswise direction of high formation density layers 2, and electrodes 4 are formed, after sintering, on both front and rear faces of the material 3. As the material 3 forming means of the above structure, oblique protrusions 10, 11 formed from the inner faces on the outer peripheral edges of pressed faces 8, 9 of upper and lower punches 6, 7 for forming a molding press mold 5 are employed to press ceramic powder 12 by the faces 8, 9. The outer surfaces are formed of the layers 2 to largely reduce the remaining strain of the outer surface at the time of sintering and to prevent microcrack from occurring at the time of application of surge. |
