A grain boundary defect model for ZnO ceramic varistors by deep heat treatment |
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Authors: | Chen Zhixiong Lin Guocong Fu Gang Tang Dahai |
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Institution: | (1) Department of Physics, Guangzhou Normal University, 510400 Guangzhou, China;(2) Department of Ultrasound, Analogic Scientific Inc., 518067 Shenzhen, China |
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Abstract: | Studies on ZnO ceramic varistors by deep heat treatment at 650–900 C are reported. The current creep time curve exhibits a
peak during the continuous action of a dc biasing voltage; the forwardV-l characteristic is improved rather than degraded after the action of the biasing voltage. We assume that the zinc interstitial
cations Zni are out diffused rapidly and the concentration of Zni in the depletion layer is decreased rapidly during deep heat treatment; the oxygen anions O’o could be accumulated at the grain interface if the out diffusion quantity of Zni is not enough to react with the O’o; the current creep phenomenon above results from the migration of the interface O’o by the biasing voltage. We suggest an improved grain boundary defect model for the ZnO varistors by deep heat treatment,
and examine the model using the experimental data of lifetime positron-annihilation spectroscopy.
Project supported by the National Natural Science Foundation of China. |
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Keywords: | ZnO ceramic varistor heat treatment grain boundary defect model current creep positron annihilation |
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