• Proceedings of the KIEE Conference
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• 1987.07a
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• pp.565-568
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• 1987

In order to determine the standard composition of ZnO varistor with higher nonlinearity, various contents of $MnO_2$, $Co_2O_3$ were added to ZnO-1.0m/o $Bi_2O_3$ system. Also, samples that contained small amount of Sb, Si-oxides in standard composition determined before were fabricated. As a result, the standard composition of higher nonlinearity-oriented ZnO varistor was shown as ZnO-1.0 m/o $Bi_2O_3$-1.0m/o $MnO_2$-1.0m/o $Co_2O_3$ and $Sb_2O_3$ largely enhanced nonlinear exponent and nonlinear resistance, hut SiO largely enhanced nonlinear exponent only.

• Proceedings of the KIEE Conference
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• 1988.11a
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• pp.359-362
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• 1988

In this papers, in order to decreased the ZnO varistor breakdown voltage, additives the $TiO_2$ with ZnO varistors. The effects of addition $TiO_2$ with ZnO varistor are discussed. Observation of ZnO varistor microstructures are photospectroscopy and SEM, and variation of phase are XRD analysis. Experimental results, the more increased the $TiO_2$ contents the more decreased the mean grain size of ZnO. Also, results of XRD analysis, the more increased the $TiO_2$ contents the more increased the spinel structures.

• Journal of the Korean Ceramic Society
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• v.37 no.7
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• pp.651-651
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• 2000

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1995.11a
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• pp.74-76
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• 1995

ZnO varistor with composition of ZnO(90wt%)-Bi$_2$O$_3$(3wt%)-Sb$_2$O$_3$(3.6wt%)-CO$_2$O$_3$(1.16wt%)-NiO(0.88wt%)-MnO$_2$(0.71wt%)-Cr$_2$O$_3$(0.93wt%) according to Al$_2$O$_3$addtive was fabricated by sintering methods. The effects of Al$_2$O$_3$dopant on the I-V characteristics of ZnO varistors were investigated. These changes of electric properties were found to be caused by the variation of grains and grain boundary related to Al$_2$O$_3$dopting. And the conductive mechanism of ZnO varistor in prebreakdown region were investigated with defect model.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.7
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• pp.662-666
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• 2006

Microstructure and electrical properties of ZnO varistors as a function of sintering temperature and times were investigated. Sintering temperature and times greatly affected electrical properties and Bi-rich liquid phase of the microstructure. The varistor which were sintered at $1125^{\circ}C\sim1150^{\circ}C$, for 2 hr exhibited the varistor voltage$(V_c)$, nonlinear coefficient $(V_{10mA}/V_{1mA})$, leakage current$(I_L)$ dielectric constant and dissipation factor as $225\sim250V/mm,\;0.89\sim0.92,\;0.8\sim1.1{\mu}A,\;720\sim740\;and\;1.8\sim2.0%$, respectively.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2166-2168
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• 2005

This paper presents the frequency - dependent characteristics of leakage currents flowing through ZnO varistor. The leakage current - voltage (V-I) characteristic curves of the commercial ZnO varistor were measured. The resistive leakage current was increased with increasing the magnitude and frequency of the applied voltage in the low conduction region. The power losses of ZnO varistor increase as the frequency of applied voltage increases, because of the dielectric loss related to the frequency of the test voltage.

• Proceedings of the KIEE Conference
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• 1996.07c
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• pp.1679-1681
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• 1996

ZnO varistor with composition of 89wt%-ZnO, 3.0wt%-$Bi_{2}O_{3}$, 3.6wt%-$Sb_{2}O_{3}$, 1.16wt%-CoO, 0.88wt%-NiO, 0.71wt%-$MnO_2$, 0.93wt%-$Cr_{2}O_{3}$, 0.013wt%-$Al_{2}O_{3}$ was fabricated by sintering methods. The effects of annealing on the J-E characteristics of ZnO varistors were investigated. These changes of electric properties were found to be caused by the variation of grains and grain boundary related to annealing. And the conductive mechanism and micostructure of ZnO varistor were researched using I-V meter, SEM and XRD.

• Proceedings of the KIEE Conference
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• 1998.07d
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• pp.1471-1474
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• 1998

ZnO Varistor with composition of ZnO, $Bi_2O_3$, $Sb_2O_3$, CoO, NiO, $MnO_2$, $Cr_2O_3$, $Al_2O_3$ was fabricated by sintering methods. The purpose of this paper is to present certified voltage-current test data and a summary of electrical characteristics of the ZnO varistors.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1989.06a
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• pp.87-92
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• 1989

We fabricated primary and secondary seed grains. Primary seed grains having larger grain size were obtained under the conditions that were 2.0m/o BaCO$_3$ and 10 hours sintering. The amount of primary seed grain to yield the largest secondary seed grains were choosed as 3 w/o and we fabricated the low voltage varistors which were joined the low voltage-oriented ZnO varistor system made by conventional method with the secondary seed grains. As a result, ZnO varistor showed appoximately 10V/mm of nonlinear resistance and 15-22 of nonlinear exponent.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.11
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• pp.876-881
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• 2011

The sintering, defect and grain boundary characteristics of Bi-based ZnO chip varistor (1,608 mm size) have been investigated to know the possibility of lowering a manufacturing price by using 100 % Ag inner-electrode. The samples were prepared by general multilayer chip varistor process and characterized by shrinkage, SEM, current-voltage (I-V), admittance spectroscopy (AS), impedance and modulus spectroscopy (IS & MS) measurement. There are no problems to make a chip varistor with 100% Ag inner-electrode in the sintering temperature range of 850~900$^{\circ}C$ for 1 h in air. A good varistor characteristics ($V_n$= 9.3~15.4 V, a= 23~24, $I_L$= 1.0~1.6 ${\mu}A$) were revealed but formed $Zn_i^{{\cdot}{\cdot}}$(0.209 eV) as dominant defect, and increased the distributional inhomogeneity and the temperature instability in grain boundary barriers.