MANUFACTURE OF GRAIN BOUNDARY BARRIER TYPE HIGH CAPACITANCE CERAMIC VARISTOR

摘要

PURPOSE:To contrive homogenization of characteristics by a method wherein perovskite type oxide powder, mainly composed of strontium titanate, is pressure-molded by adding the prescribed sintering accelerator, a semiconductivity accelerating agent, a grain growth control agent and the like. CONSTITUTION:A lamination type grain boundary barrier high electrostatic capacitance ceramic varistor 1 has an inner electrode 2 and an outer electrode 3. A sintering accelerator (0.1 to 5.0wt.%) with which a liquid-phase is principally formed at a high temperature, an accelerator for forming a semiconductor. which forms a solid solution principally in a perovskitic phase, a good oxygen conductive solid electrolyte GeO2 (0.1 to 3.0wt.%) which performs an additional function as a grain growth control agent, and a grain boundary depletion layer forming agent Sr (Mn2/3W1/3)O3(0.2 to 6.0wt.%), which performs the additional functions as a grain growth control agent, are added to and mixed with a perovskite type oxide powder mainly composed of SrTiO3, and a pressure- molding operation is conducted. Then, the molded material is sintered and reduced at 900 to 1500 deg.C. Subsequently, a heat treatment is conducted at 900 to 1150 deg.C in an oxidizing atmosphere, and electrodes 1 and 2 are formed.