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AssigneeMatsushita Electric Industrial Co., Ltd.
InventorsYoshihiro Matsuo, Masanori Fujimura, Tomizo Matsuoka, Shigeru Hayakawa
Estimating the term…
A PTC thermistor composition comprising BaTiO.sub.3, TiO.sub.2, one oxide selected from the group consisting of Nb.sub.2 O.sub.5 and Y.sub.2 O.sub.3, Al.sub.2 O.sub.3, SiO.sub.2, Li.sub.2 CO.sub.3, MnO.sub.2 and one oxide selected from the group consisting of Sb.sub.2 O.sub.3 and Bi.sub.2 O.sub.3, and process for the production thereof are provided. Said process is characterized by the addition of TiO.sub.2 and Nb.sub.2 O.sub.5 to BaTiO.sub.3 before calcination and the addition of Al.sub.2 O.sub.3, SiO.sub.2, Li.sub.2 CO.sub.3, MnO.sub.2 and Sb.sub.2 O.sub.3 after the calcination. This PTC thermistor composition has a high breakdown voltage, a large electric current at the initial moment of a voltage application which current decreases rapidly with continuing voltage application, low specific resistivity and, good stability of resistivity.
A PTC thermistor composition comprising BaTiO.sub.3 as a major element and, as additive elements 0.05 to 1.24 percent by weight of SiO.sub.2, 0.007 to 0.09 percent by weight of a lithium compound convertible by air firing to lithium oxide, 0.003 to 0.04 percent by weight of MnO.sub.2 or manganese compound convertible by air firing to a manganese oxide, and 0.05 to 0.22 percent by weight of one oxide selected from the group consisting of Nb.sub.2 O.sub.5 and Y.sub.2 O.sub.3.
A method of producing a PTC thermistor comprising preparing a mixture consisting of BaCO.sub.3 and TiO.sub.2 to be converted into 99.89 to 95.73 percent by weight of BaTiO.sub.3, less than 1.30 percent by weight of TiO.sub.2 and 0.05 to 0.22 percent by weight of one oxide selected from the group consisting of Nb.sub.2 O.sub.5 and Y.sub.2 O.sub.3, calcining the mixture at a temperature of 900 to 1250.degree.C, milling the calcined material with additives of less than 1.26 percent by weight of Al.sub.2 O.sub.3, 0.05 to 1.24 percent by weight of SiO.sub.2, 0.007 to 0.09 percent by weight of Li.sub.2 CO.sub.3, 0.003 to 0.04 percent by weight of MnO.sub.2 and less than 0.12 percent by weight of one oxide selected from the group consisting of Sb.sub.2 O.sub.3 and Bi.sub.2 O.sub.3, pressing the mixture of the calcined material and said additives into a pressed body, firing the pressed body at a temperature of 1240.degree.C to 1400.degree.C for 0.5 to 5 hours, thereafter cooling the fired body to a temperature less than 800.degree.C at a cooling rate lower than 300.degree.C per hour, and thereafter cooling the thus cooled body to room temperature.
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