• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2009년도 하계학술대회 논문집
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• pp.169-169
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• 2009

ZnO varistor에서 희토류 산화물의 첨가는 비선형계 높게 만든다. 회토류 금속의 첨가로 높아진 비저항을 낮추기 위하여 3족 원소인 Al, Ga을 첨가하여 첨가 함량에 따른 ZnO-$Pr_6O_{11}$ varistor의 비저항을 낮추고자 한다. 따라서 본 연구에서는 Al과 Ga 첨가에 따른 ZnO-$Pr_6O_{11}$을 일반적인 세라믹 공정에 따라 제조하여, Al과 Ga 첨가에 따른 ZnO-$Pr_6O_{11}$ varistor의 특성을 미세구조 조직, 밀도, I-V 특성, 비저항 측정하였다. ZnO의 bulk 및 grain boundary 특성 변화를 각종 유전함수($Z^*$, $Y^*$, $M^*$, $\varepsilon^*$, $tan{\delta}$)를 이용하여 고찰하였다.

• 한국전기전자재료학회논문지
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• 제18권1호
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• pp.50-56
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• 2005

The electrical properties, clamping voltage characteristics, and stability of dysprosia-doped ZnO-P $r_{6}$ $O_{11}$-based varistors were investigated with different dysprosia contents from 0 to 2.0 mol%. The incorporation of dysprosia in varistor ceramics greatly increased the varistor voltage from 50 to 481.0 V/mm. It was found that the dysprosia is good additive improving a nonlinearity, in which the nonlinear exponent is above or near 50, and the leakage current is below 1.0 $\mu$A. The dysprosia-doped varistors exhibited superior clamping voltage characetristics, in which clamping voltage ratio is above or neat 2 at surge current of 50 A. The 0.5 mol% dysprosia-doped varistors only exhibited high stability, with the rate of varistor voltage of -0.9%, under DC acceleraetd aging stress, 0.95 $V_{lmA}$/15$0^{\circ}C$/24 h.h.h.h.

• 마이크로전자및패키징학회지
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• 제7권3호
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• pp.7-11
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• 2000

공침법을 이용하여 제조한 $SrTiO_3$분말에 $CuO-SiO_2$첨가물을 혼합하여 저전압구동형 SrTiO$_3$세라믹 바리스터 소자를 제조하였다. $CuO-SiO_2$첨가물을 이용한 $SrTiO_3$세라믹 바리스터제조 공정은 복잡한 공정을 단순화시킬 수 있을 뿐만 아니라, 일반적인 소결온도보다 100~$150^{\circ}C$ 낮은 온도에서도 소결이 되었다. 이 바리스터의 비직선계수($\alpha$) 값은 첨가물 5 wt% 혼합하여 $1350^{\circ}C$에서 하소한 시편에서 8.47의 최고값을 나타냈으며, 이때의 구동전압은 7 V 이하로 낮은 구동전압을 가진 바리스터를 제조할 수 있었다.

• 한국전기전자재료학회논문지
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• 제20권6호
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• pp.496-501
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• 2007

In order to enhance sintering characteristics on the $ZnO-Pr_6O_{11}$ based multilayer chip varistors (MLVs), a response surface analysis using central composite design method were carried out. As a result, varistor voltage($V_{1mA}$), nonlinear coefficient ($\alpha$), leakage current ($I_L$) and capacitance (C) were considered to be mainly affected by sintered temperature and holding time. MLVs sintered at $1200^{\circ}C$ and above $1200^{\circ}C$ revealed poor electrical characteristics, possibly due to the reaction between electrode materials(Pd) and $ZnO-Pr_6O_{11}$ based ceramics. On the sintering temperature range $1150{\sim}1175^{\circ}C$, nonlinear coefficient ($\alpha$) and leakage current ($I_L$) were shown to be $60{\sim}69$ and below $0.3{\mu}A$, respectively. In particular, MLVs sintered at $1175^{\circ}C$, 1.5 hr and $2^{\circ}C/hr$ (cooling speed) showed stable ESD(Electrical Static Discharge) characteristics under the condition of 10 times at 8 Kv with deviation varistor voltage, and deviation nonlinear coefficient were 0.3% and 0.33% (at positive), 0.55% (at negative), respectively.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2004년도 추계학술대회 논문집 전기물성,응용부문
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• pp.67-69
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• 2004

ZnO varistor ceramics which were fabricated with variation of added of 0.01, 0.02, 0.03, 0.05, 0.1mol% $Nb_2O_5$ sintered at $1150^{\circ}C$. In the specimen added 0.05mol% $Nb_2O_5$, sintered density was $5.87g/cm^3$ and electrical properties were superior to any other components. The nonlinear coefficient was 75, and clamping voltage ratio was 1.40. And, endurance surge current in the specimen added 0.05mol% $Nb_2O_5$ was $6500A/cm^2$, and deviation of varistor voltage was -1.7%. As P.C.T and T.C.T environment test were succeed in all specimens, and deviation of varistor voltage in the specimen added 0.3mol% $Nb_2O_5$ was -0.81%. All specimens showed a good leakage current property in the High Temperature Continuous Load Test for 1000hr, at $85^{\circ}C$, and variation rate of the varistor voltage was -1.71%.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2005년도 하계학술대회 논문집 Vol.6
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• pp.336-337
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• 2005

ZnO varistor ceramics were fabricated as a function of the amount of $Y_2O_3$ addition and sintered at $1250^{\circ}C$ for 2 hour. The average grain size was decreased from 14.2 ${\mu}m$ to 8.3 ${\mu}m$ with the amount of $Y_2O_3$ addition, and varistor voltage was increased from 433 V to 563 V with $Y_2O_3$ addition. Nonlinear coefficient a of all specimens were increased with the amount of $Y_2O_3$ more than 67, in case of $Y_2O_3$ 0.01wt% addition showed the excellent results of 87. And leakage current was less than $1{\mu}A$ at 82% of varistor voltage. The clamping voltage ratio of the specimens added 0.01wt% $Y_2O_3$ was 1.41 at 25A [8/20${\mu}s$]. At the specimen 0.01wt% $Y_2O_3$ addition. endurance of surge current and deviation of varistor voltage were 5700A/$cm^2$ and $\Delta$-2.86%, respectively.

• 한국결정성장학회지
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• 제17권2호
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• pp.63-68
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• 2007

EMI filter와 같은 적층형 세라믹 제조 시 공정 상 많은 문제점이 야기된다. 특히 표면과 계면에서의 crack, camber, delamination 같은 결함이 없는 적층체를 얻기 위해 서로 다른 두 재료의 동시 소성에 의한 수축율 조절이 필수적이다. 본 연구에서는 ferrite의 분체 특성을 통해 varistor/ferrite의 동시소성 거동을 연구하였다. ferrite 분말을 각각 24시간, 48시간, 72시간 분쇄하여 varistor와 ferrite 각각의 슬러리를 제조하고 doctor blade법으로 green sheet를 제조하였다. 슬러리는 분말 55wt(%)에 binder solution 45wt(%)로 혼합하여 제조하였다. Varistor와 ferrite green sheet는 $80 kg/cm^2$로 적층하여 $900^{\circ}C$, $1000^{\circ}C$에서 3시간 소결 하였다. 그 결과 분쇄시간과 소결온도 조절로 결함이 없는 동시 소성된 ferrite/varistor 적층체를 제조 할 수 있었다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 1987년도 전기.전자공학 학술대회 논문집(I)
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• pp.385-388
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• 1987

• E2M - 전기 전자와 첨단 소재
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• 제8권1호
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• pp.40-47
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• 1995

Electrical properties of ZnO ceramics based on Bi oxide was investigated in relation to sintering temperature. In the temperature range >$1150^{\circ}C$ to >$1350^{\circ}C$ the grain size increased from 9.mu.m to 20.mu.m when the sintering temperature was raised. The leakage current in the low voltage range increased as the potential barrier decreases, which is caused by increasing the grain size at high temperature. The dielectric characteristics of the ZnO ceramics was also affected by sintering temperature. Large dielectric constant was attributed, to the grainboundary layer of polycrystalline ZnO ceramics and decreasing grainboundary width. The variation of breakdown voltage with sintering temperature was attributed to the change of the donor concentration in the ZnO grain and grain size. The results showed that breakdown voltage increased decreasing grain size and donor concentration. Nonohmic coefficient was associated with the lower breakdown voltage per grainboundary layer due to the grain growth and higher donor concentration.

• 한국세라믹학회지
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• 제19권4호
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• pp.287-292
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• 1982

Nonohmic properties of ZnO ceramics with various small amounts of additives were studied in relation to experimental methods, additive contant and sintaring temperature. The kinds of additives used to following chemicals were basic additives ($0.5Bi_2O_3$, $0.3BaCO_3$, $0.5MnCO_3$, $0.5Cr_2O_3$, $0.1KNO_3$), $TiO_2$ and $Al(OH)_3$. Expecially, this study has focused on the effectsof $TiO_2$ and $Al(OH)_3$ in ZnO ceramics with the basic additives. SEM studies indicated that the addition of TiO2 promoted grain growth but retarded grain growth with the addition of $Al(OH)_3$. Also, in the case of calcination of ZnO with $TiO_2$ and ZnO with $Al(OH)_3$ previously, grain size of ZnO with $TiO_2$ was larger and that of ZnO with Al(OH)3 was smaller in comparison to the case with out calcination. From the viewpoint of nonohmic exponent and nonohimic resistance, electrical characteristics of ZnO, $TiO_2$ and the basic additives was more effective than that of ZnO, $Al(OH)_3$ and the basic additives. Nonohmic exponent and nonohmic resistance of ZnO, $TiO_2$ and the basic additives was 11-13 and 40-65 respectively.