Fabrication and operation limit of lead-free PTCR ceramics using BaTiO sub(3)-(Bi sub(1/2)N a sub(1/2))TiO sub(3) system

The electric properties of BaTiO sub(3)-(Bi sub(1/2)N a sub(1/2))TiO sub(3) (BT-BNT) solid solution ceramics were studied as a lead-free PTCR (positive temperature coefficient of resistivity) thermistor material usable over 130 degree C. For determining the maximum switching temperature T sub(s), th...

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Bibliographic Details
Published in:Journal of electroceramics 2009-02, Vol.22 (1-3), p.263-269
Main Authors: Takeda, Hiroaki, Shimada, Takeshi, Katsuyama, Yoshiaki, Shiosaki, Tadashi
Format: Article
Language:English
Subjects:
Ceramics
Dielectrics
Electrical resistivity
Phase diagrams
Positive temperature coefficient
Solid solutions
Switching
Thermistors
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Summary:The electric properties of BaTiO sub(3)-(Bi sub(1/2)N a sub(1/2))TiO sub(3) (BT-BNT) solid solution ceramics were studied as a lead-free PTCR (positive temperature coefficient of resistivity) thermistor material usable over 130 degree C. For determining the maximum switching temperature T sub(s), the phase diagram of BT-BNT binary system was clarified. Two semiconductorization processes and their electric properties are described. The lanthanum(La)-doped BBNT ceramics sintered in air still showed dielectric behaviors, but the niobium(Nb)-doped ones had a low resistivity at room temperature, rho sub(RT), on the order of 10 super(3) Omega cm and showed a PTC behavior. Sintering under a low O sub(2) atmosphere produces BT-BNT ceramics with less than 10 super(2) Omega cm compared to those prepared in air. Our current research produced the BBNT ceramics with T sub(s) values around 210 degree C by increasing the (Bi sub(1/2)Na sub(1/2)) content in the ceramics.
ISSN:1385-3449
1573-8663
DOI:10.1007/s10832-007-9398-6