• 한국세라믹학회지
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• 제56권1호
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• pp.84-90
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• 2019

The varistor properties and stability against dc-accelerated stress of $V_2O_5-Mn_3O_4-Co_3O_4-Dy_2O_3-Nb_2O_5-Bi_2O_3$ (VMCDNB)-doped zinc oxide ceramics sintered at $850-925^{\circ}C$ were investigated. Increasing the sintering temperature increased the average grain size from 4.6 to 8.7 mm and decreased the density of the sintered pellet density from 5.54 to $5.42g/cm^3$. The breakdown field decreased from 5919 to 1465 V/cm because of the increase in the average grain size. Zinc oxide ceramics sintered at $875^{\circ}C$ showed the highest nonlinear coefficient (43.6) and the highest potential barrier height (0.96 eV). Zinc oxide ceramics sintered at $850^{\circ}C$ showed the highest stability: the variation rate of the breakdown field was -2.0% and the variation rate of the nonlinear coefficient was -23.3%, after application of the specified stress (applied voltage/temperature/time).

• 조명전기설비학회논문지
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• 제20권8호
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• pp.22-29
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• 2006

IEC 규격을 기반으로 최근에 개정된 KS 규격에 따라 등전위 접지시스템이 중요하게 자리매김 하였으며, 전원시스템의 안정성을 위해 서지보호소자의 사용이 급격히 증가하고 있다. 내재된 비선형 저항성분으로 뛰어난 V-I 특성을 가지는 $Z_nO$ 바리스터는 서지전압을 제한하여 서지전류로 환류시키기 위해 전원용 보호기로 주로 사용되고 있다. 이러한 $Z_nO$ 바리스터는 교류 전원선에 접속하기 위해서 몇 가지 회로조합 형태로 구성되어 사용되는데, 사용자는 바리스터를 직렬 혹은 병렬로 조합하여 사용함에 있어서 안전에 직접적으로 관련된 기능이나 열적 안정성을 포함한 많은 것들을 고려하여야 한다. 본 논문에서는 40[kA]의 전류용량을 가지는 단일 바리스터 소자와 직렬 혹은 병렬 회로조합의 바리스터에 대하여 잔류전압, 방전전류, 누설전류, 표면온도를 측정하여 각각의 조합형태에 따라 안정성을 비교하였다.

• The Korean Journal of Ceramics
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• 제5권4호
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• pp.357-362
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• 1999

ZnO varistors containing cobalt, praseodymium and calcium oxides were prepared. The current-voltage charcteristics and microstructures of the specimens were investigated with respect to calcium addition and sintering temperature. The potential barrier heights and the carrier densities were estimated from C-V relations. The compatibility of Ag-Pd as an internal electrode for multilayer chip varistor was also examined.

• 전기의세계
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• 제31권6호
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• pp.445-449
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• 1982

This Paper describes the influence of additive concentrations and sintering temperature on the surge protection performance in ZnO ceramic varistors. It is found from the experiments that the metal-oxide semiconductors based oi ZnO with an additive incorporation of 0.50% molx(Bi$\_$2/O$\_$3/+MnO+CoO+Cr$\_$2/O$\_$3/+2Sb$\_$2/O$\_$3/) and sintered at 1250.deg. C present excellent V-I characteristics in view of transient surge suppression. Gapless arrester element with aluminum electrodes shows also good reliability against impulse shock and marks a low voltage clamping ratio(V$\_$1KA/V$\_$1mA/<2.0) compared with the conventional SiC varistors.

• 한국전기전자재료학회논문지
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• 제21권7호
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• pp.652-659
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• 2008

The nonlinear electrical properties and aging characteristics against surge stress of ZPCCL-based varistors were investigated for different sintering temperatures of the range $1240-1300^{\circ}C$. As the sintering temperature increased, the varistor voltage decreased from 732.2 to 53.8 V/mm, the nonlinear exponent decreased from 58.5 to 4.1, and the leakage current increased from $0.38{\mu}A$ to $46.5{\mu}A$. The varistors sintered at $1250^{\circ}C$ and $1260^{\circ}C$ exhibited the high stability against multiple surge, $150A/cm^2(8{\times}20{\mu}s)$. On the whole, the variation rate of electrical characteristics against impulse current stress was gradually increased in order of varistor voltage$\rightarrow$nonlinear exponent$\rightarrow$dissipation facto$\rightarrow$leakage current.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2001년도 하계학술대회 논문집
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• pp.410-414
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• 2001

The microstructure, V-I characteristics, and stability of ZnO-Pr$_{6}$O$_{11}$-CoO-Cr$_2$O$_3$-Y$_2$O$_3$based vairstors were investigated with cooling rate in the range of 2~8$^{\circ}C$/min. The cooling rate relatively weakly affected the microstructure, and the varistor voltage and the leakage current in the V-I chracteristics. But the nonlinear exponent relatively strongly affected by cooling rate. And the cooling rate also greatly affected the stability for DC stress. In gross, the varistors cooled with 4$^{\circ}C$/min exhibited the highest performance in the densification, nonlinearity, and stability. Especially, they exhibited a high stability, in which the variation rate of the varistor voltage and the nonlinear exponent is -1.44% and -4.85%, respectively, under more severe DC stress such as (0.80 V$_{1mA}$9$0^{\circ}C$/12 h)+(0.85 V$_{1mA}$115$^{\circ}C$/12 h)\`(0.90 V$_{1mA}$12$0^{\circ}C$/12 h)+(0.95 V$_{1mA}$1$25^{\circ}C$/12 h)+(0.95 V$_{1mA}$15$0^{\circ}C$/12 h). It should be emphasized that the stability of these varistors is much superior to that of others.s.of others.s.

• 한국전기전자재료학회논문지
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• 제14권8호
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• pp.640-646
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• 2001

The electrical stability for DC stress of Pr$_{6}$O$_{11}$-based ZnO varistos consisting of ZnO-Pr$_{6}$O$_{11}$-CoO-Cr$_2$O$_3$-Er$_2$O$_3$-based ceramics were investigated with sintering temperature in the range of 1325~1345$^{\circ}C$. A the sintering temperature is raised, the nonlinear exponent of varistors was decreased, whereas the stability was markedly improved. The density of ceramics was found to greatly affect the electrical stability for DC stress. The varistors sintered at 13$25^{\circ}C$ were completely degraded because of thermal runaway attributing to low density. The varistors sintered at 1335$^{\circ}C$ exhibited the highest nonlinearity, with a nonlinear exponent of 70.53 and a leakage current of 1.92$\mu$A, whereas they did not exhibit relatively high stability. On the contrary, the varistors sintered at >134$0^{\circ}C$ exhibited not only a high nonlinearity marking the nonlinear exponent above 50 and the leakage current below 3$\mu$A, but also a high stability marking the variation rate of the varistor voltage below 2%, even under DC stress such as (0.80V$_{1mA}$/9$0^{\circ}C$/12h)+(0.85V$_{1mA}$/115$^{\circ}C$/12h)+(0.90V$_{1mA}$/12$0^{\circ}C$/12h)+(0.95V$_{1mA}$/1$25^{\circ}C$/12h)+(0.95V$_{1mA}$/15$0^{\circ}C$/12h). In particular, ti was found that the varistors sintered at 134$0^{\circ}C$ were more nonlinear and more stable, compared with that of 1345$^{\circ}C$.EX>.}C$.EX>.

• 한국전기전자재료학회논문지
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• 제16권1호
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• pp.39-45
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• 2003

The varistor properties of ZnO-Pr$_{6}$O$_{11}$-CoO-based ceramics doped with Sm$_2$O$_3$were investigated in the addition range of 0.0~2.0 mol% Sm$_2$O$_3$at sintering temperature of 130$0^{\circ}C$ and 135$0^{\circ}C$. As Sm$_2$O$_3$ content is increased, the breakdown voltage was increased in the range of 348.9~521.8 V/mm for ceramics sintered at 130$0^{\circ}C$ and 8.5~381.3 V/mm for ceramics sintered at 135$0^{\circ}C$. On the whole, the increase of sintering temperature led to the low nonlinearity regardless of Sm$_2$O$_3$content. ZnO-Pr$_{6}$O$_{11}$-CoO-based ceramics doped with 1.0 mol% at each sintering temperature exhibited the most superior varistor properties, with the nonlinear exponent of 42.1 at 130$0^{\circ}C$, 36.8 at 135$0^{\circ}C$ and the leakage current of 9.2 $\mu$A at 130$0^{\circ}C$, 11.7 $\mu$A at 135$0^{\circ}C$.EX>.EX>.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1999년도 추계학술대회 논문집 학회본부 C
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• pp.1003-1007
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• 1999

This paper is reported for the stability of ZnO-$Pr_{6}O_{11}-CoO-Er_{2}O_{3}$ based ceramic varistors with $Er_{2}O_{3}$ added in the addition range 0.0 to 2.0 mol%. The varistors sintered at $130^{\circ}C$ exhibited abrupt positive current creep phenomena, which accompany thermal run away within short times, even under weak d.c. stress. As a result, these varistors were completely degraded. On the contrary, the stability of varistors sintered at $1350^{\circ}C$ was far better than that of $1300^{\circ}C$. In particular, the varistor containing 0.5 mol% $Er_{2}O_{3}$ showed a excellent stability, which the variation rate of the varistor voltage, the nonlinear coefficient, and leakage current is below 1%, 2%, and 3.5%, respectively, even under more severe d.c. stress, such as ($0.8V_{1mA}/90^{\circ}C/12h$) + ($0.85V_{1mA}/115^{\circ}C/12h$) + ($0.9V_{1mA}/120^{\circ}C/12h$) + ($0.9V_{1mA}/150^{\circ}C/12h$). Consequently, it is estimated that the basic composition of ZnO-$Pr_{6}O_{11}-CoO-Er_{2}O_{3}$ based varistor contain 0.5 mol% $Er_{2}O_{3}$ will be used to the fabrication of the varistors for high performance and stability in a forthcoming.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.330-333
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• 2002

The stability against DC accelerated aging stress of $Dy_{2}O_{3}-doped$ $ZnO-Pr_{6}O_{11}-based$ varistor ceramics was investigated. The calculated nonlinear exponent$(\alpha)$ in varistor ceramics without $Dy_{2}O_{3}$ was only 4.9, whereas the $\alpha$ value of the varistors with $Dy_{2}O_{3}$ was abruptly increased in the range of 48.8 to 58.6. The varistor ceramics with $Dy_{2}O_{3}$ content of 1.0 mol% exhibited maximum ${\alpha}$, reaching 58.6, whereas they exhibited very poor stability. While, The varistor ceramics doped with 0.5 mol% $Dy_{2}O_{3}$ exhibited not only the high nonlinearity, which the ${\alpha}$ is 55.3 and the leakage current is $0.1{\mu}A$， but also the highest stability, which the variation rates of varistor voltage and nonlinear exponent are -0.8% and -14.3%, respectively, under DC accelerated aging stress, $0.95 V_{1mA}/150^{\circ}C/24h$.