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Grain boundary effects in NTC-PTC composite thermistor materials

Published online by Cambridge University Press:  26 July 2012

D. J. Wang ,
J. Qiu ,
Y. C. Guo ,
Z. L. Gui  and
L. T. Li
D. J. Wang
Affiliation:
State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
J. Qiu
Affiliation:
State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
Y. C. Guo
Affiliation:
State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
Z. L. Gui
Affiliation:
State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
L. T. Li
Affiliation:
State Key Laboratory of New Ceramics and Fine Processing, Department of Materials Science and Engineering, Tsinghua University, Beijing 100084, China
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Extract

Yttrium-doped (Sr0.45Pb0.55)TiO3 ceramics have been studied by complex impedance analysis. As a sort of NTC-PTC composite thermistor, it exhibited a significantly large negative temperature coefficient of resistivity below Tc in addition to the ordinary PTC characteristics above Tc. It is found that the NTC effect in NTC-PTC materials was not originated from the deep energy level of donor (bulk behavior), but from the electrical behavior of the grain boundary. Therefore, the NTC-PTC composite effect was assumed to be a grain boundary effect, and yttrium was a donor at shallow energy level. The NTC-PTC ceramics were grain boundary controlled materials.

Type
Articles
Information
Journal of Materials Research , Volume 14 , Issue 1 , January 1999 , pp. 120 - 123
Copyright
Copyright © Materials Research Society 1999

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References

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