Results 181 to 190 of about 2,053 (224)

Phase development in ZnO varistors

Advances in Applied Ceramics, 2014
Based on a typical ZnO varistor composition (97·0 mol.-% ZnO, 1·0 mol.-% Bi2O3, 1·0 mol.-% Sb2O3, 0·5 mol.-% MnO and 0·5 mol.-% Co3O4), phase development of the ZnO varistor during sintering has been investigated using in situ high temperature X-ray diffraction up to 900°C, and conventional ambient X-ray diffraction for samples sintered at 900°C to ...
Fan, J, Poosimma, P, Freer, Robert
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Prebreakdown Conduction in ZnO Varistors

Journal of the American Ceramic Society, 1992
A model which quantitatively accounts for the important features of prebreakdown conduction in ZnO‐based metal oxide varistors in presented. The prebreakdown current dependence with applied voltage and temperature enables us to extract several features for the grain boundary.
Miriam S. Castro, Guillermo M. Nuñez, Daniel E. Resasco, Celso M. Aldao   +3 more
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Impulse current withstanding capability of ZnO varistors with influence of varistor size

IEEJ Transactions on Electrical and Electronic Engineering, 2019
Through injecting 8/20 and 30/60 μs impulse currents to five kinds of ZnO varistors, the influence of the varistor size on the single impulse current withstanding capability of a ZnO varistor is investigated in this article. A comprehensive damage criterion of a varistor consisting of three aspects, namely, mechanical failure by visual inspection ...
Jianguo Wang, Linmao Mei, Wanlu Su, Xu Wang, Mi Zhou, Yadong Fan   +5 more
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Evaluation of ZnO Varistors by Photoacoustic Spectroscopy

Japanese Journal of Applied Physics, 2001
ZnO varistors degraded under various conditions were evaluated by photoacoustic spectroscopy (PAS). The degradation where the grain boundary is damaged by DC bias stress is more than that by AC bias stress. PAS, however, reveals that the interior of the grains of the sample degraded by AC bias stress is much more damaged than that by the DC bias ...
Yasuhiro Ohbuchi Yasuhiro Ohbuchi, Akitsugu Kimura Akitsugu Kimura, Toshio Kawahara Toshio Kawahara, Jun Morimoto Jun Morimoto, Taro Toyoda Taro Toyoda   +4 more
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Varistor-capacitor characteristics of ZnO ceramics

Journal of Materials Science, 1986
Electrical properties of ZnO ceramics quenched from several temperatures during the cooling down from sintering temperature were correlated with microstructural changes. Barrier parameters were determined and their variation was interpreted under the assumption that measured donor densities were due to extrinsic donor defects segregated at grain ...
P. Q. Mantas, A. M. R. Senos, J. L. Baptista   +2 more
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Intrinsic defects in ZnO varistors

Journal of Applied Physics, 1983
Theoretical calculations are presented for equilibrium concentrations of zinc and oxygen vacancies in ZnO. Results are presented at the sintering temperature, and also at room temperature. Theoretical calculations of reaction constants show that the intrinsic donor is the oxygen vacancy, rather than the zinc interstitial.
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Metastable Barrier Voltage in ZnO Varistors

MRS Proceedings, 1981
ABSTRACTA reversible change in barrier voltage is observed in assintered ZnO varistors upon application and removal of the applied voltage. This is attributed to a metastable component in the grain boundary Schottky barriers. Varistors show improved stability when the metastable component is removed or fixed by heat treatment.
Tapan K. Gupta, William G. Carlson, Barbara O. Hall   +2 more
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Ceramic varistors based on ZnO–SnO2

Journal of the European Ceramic Society, 2004
Abstract Model ceramic varistor formulations based on 98% ZnO–SnO2 (plus 2% oxides of Bi, Co and Mn) were prepared by conventional powder processing routes; specimens were sintered at 1150–1275 °C. The product density increased with SnO2 content, but decreased with increase in sintering temperature.
A. Anastasiou, M.H.J. Lee, C. Leach, R. Freer   +3 more
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Rate-controlled shrinkage of ZnO varistors

Journal of Materials Processing Technology, 1996
Abstract Shrinkage of ZnO varistors has been controlled during the firing process at a constant rate using a feed back loop to control the heating rate. This was accomplished by developing software which calculates the shrinkage from a signal coming from a displacement transducer, then it compares the current shrinkage rate with a previously set ...
A. Al-Tounsi, R. Puyané, M.S.J. Hashmi
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Impedance and Modulus Spectroscopy of ZnO Varistors

Journal of Electroceramics, 1997
The ac response of ZnO varistors has been investigated over thetemperature range 100 to 380°C using impedance and modulusspectroscopy. Impedance spectra show only a single peak, which representsthe most resistive component in the sample and is responsible for the dcproperties, whereas an additional peak appears in the modulus spectrum.
A.R. West, M. Andres-Verges
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