| 摘要 |
PURPOSE:To enable the title element to indicate a positive or zero value in the temperature coefficient of varistor voltage and to improve temperature characteristics, reliability, and lifetime characteristics through suppression of its directionalities by mixing an oxide having a perovskite structure whose main components are Si and Ti atoms with a 0.2-5.0mol% of NaAlO2. CONSTITUTION:Electrodes 2, 3 are formed on a sinter 1 prepared from disc molding and baking of a stock that is a mixture granulation of SrTiO3, NP2O5 a valence controller, and NaAlO2 for improving the temperature coefficient of varistor voltage. In general a capacitive varistor prepared from addition of a valance controller such as Nb, Ta to SrTiO3 and baking of the mixture shows difference in the degree of reoxidation between the surface and inside of the element, thereby decreasing varistor voltage and easily generating directionalities. Therefore, addition of NaAlO2 and baking of the mixture as a method for eliminating this asymmetric energy barrier can produce uniform reoxidation inside the element and suppress the gradient of oxygen concentration. This process can suppress the varistor voltage decreases and directionalities and improve temperature characteristics, reliability, and lifetime characteristics. |
