Method of manufacturing ceramics for positive temperature coefficient thermistor

摘要

The object of the present invention is to provide a ceramic for the PTC thermistor having a resistivity at room temperature of 5 OMEGA .cm or less, static withstanding voltage of 60 V/mm or more and temperature resistance coefficient of 9.0 %/ DEG C along with having small dispersion of the resistance, wherein the ceramic for the PTC thermistor is composed of principal components of 30 to 97 molar percentage (mol%) of BaTiO3, 1 to 50 mol% of PbTiO3, 1 to 30 mol% of SrTiO3 and 1 to 25 mol% of CaTiO3 (the total content of them accounts for 100 mol%), as well as 0.1 to 0.3 mole of samarium oxide in terms of Sm element, 0.01 to 0.03 mole of manganese oxide in terms of Mn element and 0 to 2.0 mole of silicon oxide in terms of Si element relative to 100 moles of the principal components, the composite material being preferably heat-treated in an oxidative atmosphere after being fired in a reducing atmosphere for obtaining the ceramic.