PTC thermistor composition and method of making the same
First Claim
1. A PTC thermistor composition comprising BaTiO3 as a major element and, as additive elements 0.05 to 1.24 percent by weight of SiO2, 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 MnO2 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 Nb2 O5 and Y2 O3.
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Abstract
A PTC thermistor composition comprising BaTiO3, TiO2, one oxide selected from the group consisting of Nb2 O5 and Y2 O3, Al2 O3, SiO2, Li2 CO3, MnO2 and one oxide selected from the group consisting of Sb2 O3 and Bi2 O3, and process for the production thereof are provided. Said process is characterized by the addition of TiO2 and Nb2 O5 to BaTiO3 before calcination and the addition of Al2 O3, SiO2, Li2 CO3, MnO2 and Sb2 O3 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.
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Citations
16 Claims
- 1. A PTC thermistor composition comprising BaTiO3 as a major element and, as additive elements 0.05 to 1.24 percent by weight of SiO2, 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 MnO2 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 Nb2 O5 and Y2 O3.
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16. A method of producing a PTC thermistor comprising preparing a mixture consisting of BaCO3 and TiO2 to be converted into 99.89 to 95.73 percent by weight of BaTiO3, less than 1.30 percent by weight of TiO2 and 0.05 to 0.22 percent by weight of one oxide selected from the group consisting of Nb2 O5 and Y2 O3, calcining the mixture at a temperature of 900 to 1250°
- C, milling the calcined material with additives of less than 1.26 percent by weight of Al2 O3, 0.05 to 1.24 percent by weight of SiO2, 0.007 to 0.09 percent by weight of Li2 CO3, 0.003 to 0.04 percent by weight of MnO2 and less than 0.12 percent by weight of one oxide selected from the group consisting of Sb2 O3 and Bi2 O3, pressing the mixture of the calcined material and said additives into a pressed body, firing the pressed body at a temperature of 1240°
C to 1400°
C for 0.5 to 5 hours, thereafter cooling the fired body to a temperature less than 800°
C at a cooling rate lower than 300°
C per hour, and thereafter cooling the thus cooled body to room temperature.
- C, milling the calcined material with additives of less than 1.26 percent by weight of Al2 O3, 0.05 to 1.24 percent by weight of SiO2, 0.007 to 0.09 percent by weight of Li2 CO3, 0.003 to 0.04 percent by weight of MnO2 and less than 0.12 percent by weight of one oxide selected from the group consisting of Sb2 O3 and Bi2 O3, pressing the mixture of the calcined material and said additives into a pressed body, firing the pressed body at a temperature of 1240°
Specification
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- Resources
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Current AssigneeMatsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
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Original AssigneeMatsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
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InventorsMatsuo, Yoshihiro, Hayakawa, Shigeru, Matsuoka, Tomizo, Fujimura, Masanori
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Primary Examiner(s)Padgett, Benjamin R.
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Assistant Examiner(s)Parr, E. Suzanne
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Application NumberUS05/513,474Time in Patent Office678 DaysField of Search252/518, 252/521, 252/520, 106/73.31, 106/73.32, 106/73.3US Class Current252/520.21CPC Class CodesH01B 1/08 oxidesH01C 1/1406 Terminals or electrodes for...H01C 7/025 Perovskites, e.g. titanatesH05B 3/141 Conductive ceramics, e.g. m...
