Results 181 to 190 of about 2,304 (224)
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Evaluation of ZnO Varistors by Photoacoustic Spectroscopy
Japanese Journal of Applied Physics, 2001ZnO 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 +4 more
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Varistor-capacitor characteristics of ZnO ceramics
Journal of Materials Science, 1986Electrical 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 +2 more
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Intrinsic defects in ZnO varistors
Journal of Applied Physics, 1983Theoretical 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, 1981ABSTRACTA 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 +2 more
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Ceramic varistors based on ZnO–SnO2
Journal of the European Ceramic Society, 2004Abstract 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 +3 more
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Rate-controlled shrinkage of ZnO varistors
Journal of Materials Processing Technology, 1996Abstract 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, 1997The 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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Cooling rate effects in ZnO varistors
Journal of Materials Science: Materials in Electronics, 1992Cooling rate effects on ZnO-Bi2O3 varistors are presented. In particular, the oxygen vacancies (V o + ) concentration was determined by electron paramagnetic resonance (EPR) spectroscopy and related to the conductivity. It was found that a higher cooling rate provokes an increase of the V
M. S. Castro +2 more
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Pulse response characteristics of ZnO varistors
Journal of Applied Physics, 1990A study is reported of the influences of temperature, circuit resistance, and pulse repetition rate on the ZnO varistor inductive pulse response that is disclosed by voltage overshoot and current undershoot. Exponential time constants are fitted to the voltage overshoot and the current undershoot obtained by using high- and low-impedance pulse supplies,
F. A. Modine, R. B. Wheeler
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Advances in ZnO–Bi2O3 based varistors
Journal of Materials Science: Materials in Electronics, 2015In this review paper detailed development of the ZnO–Bi2O3 based polycrystalline varistors are presented as the technological importance emerged with the rapid applications of the gapless surge protectors superseding traditional gapped SiC designs. The excellent symmetric nonlinear current–voltage (I–V) characteristic of these varistors results from ...
Jianying Li +3 more
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