• Title, Summary, Keyword: DC accelerated aging stress

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Effect of Sintering Temperature on Electrical and Dielectric Behavior of Pr6O1-Based ZnO Varistors with DC Accelerated Aging Stress (Pr6O1계 ZnO 바리스터의 DC 가속열화 스트레스에 따른 전기적, 유전적 거동에 미치는 소결온도의 영향)

  • 남춘우;정영철;김향숙
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.3
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    • pp.244-252
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    • 2002
  • The electrical and dielectric behavior fort DC accelerated aging stress of P $r_{6}$ $O_{11}$-based Zno varistors cnsisting of ZnO-P $r_{6}$ $O_{11}$-CoO-C $r_2$ $O_3$-E $r_2$ $O_3$ were investigated with sintering temperature in the range of 1325~1345$^{\circ}C$. The varistor ceramics with increasing sintering temperature were more densified. A more densified varistors leaded to high stability for DC accelerated aging stress. Furthermore, the stability for DC accelerated aging stress was increased with the leakage current and dtan $\delta$/dV decreasing in order of 1325longrightarrow1335longrightarrow1345longrightarrow134$0^{\circ}C$ in sintering temperature. It was found that the stability for DC stress is affected more greatly by the leakage current and dtan $\delta$/dV than the densification. It is considered that the stability of varistors for DC stress can be estimated by considering the factors, such as the densification, leakage current, and dtan $\delta$/dV. As a result, the varistor sintered at 134$0^{\circ}C$ exhibited the highest stability, with %$\Delta$ $V_{lmA}$=-1.54%, %$\Delta$$\alpha$=-2.49%, %$\Delta$ $I_{\ell}$=+240.68%, 5%$\Delta$tan$\delta$=+29.96%.96%.96%.%.

DC Accelerated Aging Characteristics of ZPCCL-Based Varistor Ceramics (ZPCCL계 바리스터 세라믹스의 DC 가속열화특성)

  • Kim, Hyang-Suk;Nahm, Choon-Woo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.629-633
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    • 2002
  • The degradation behaviour of ZPCCL-based varistor ceramics composed of 97.5 mol%ZnO-0.5 mol% $Pr_6O_{11}-1.0$ mol% $Cr_2O_3-0.5$ mol% $La_2O_3$ was investigated under various DC accelerated aging streses. The varistor ceramics sintered for 1 h exhibited excellent nonlinearity, in which the nonlinear exponent is 81.6 and the leakage current is $0.2{\mu}A$. It was found that this varistor ceramics possess high stability, in which the variation rates of varistor voltage, nonlinear exponent, and leakage current are -1.14%, -3.7%, and 85.0%, respectively, against DC accelerated aging stress. On the contrary, the varistor ceramics sintered for 2 h also exhibited high nonlinearity and stability, but they were bad characteristics, compared with the varistor ceramics sintered for 1 h.

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Effect of Cooling Rate on DC Accelerated Aging Characteristics of ZPCCY-Based Varistor Ceramics (ZPCCY계 바리스터 세라믹스의 DC 가속열화 특성에 미치는 냉각속도의 영향)

  • 남춘우;김향숙
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.15 no.9
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    • pp.776-782
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    • 2002
  • The microstructure, V-Ι characteristics, and stability of ZnO-P $r_{6}$ $O_{11}$ CoO-C $r_2$ $O_3$- $Y_2$ $O_3$-based varistor ceramics were investigated with cooling rate in the range of 2~8$^{\circ}C$/min. The cooling rate relatively weakly affected the microstructure, the varistor voltage, and the leakage current in the V-Ι characteristics. But the nonlinear exponent relatively strongly affected by cooling rate. The cooling rate also greatly affected the stability of V-Ιand dielectric characteristics for DC accelerated aging stress. On the whole, the varistors cooled with 4$^{\circ}C$/fin 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( $V_{1㎃}$), the nonlinear exponent($\alpha$), and the dissipation factor(tan $\delta$) is -1.4%, -4.9%, and +60.0%, respectively, under DC accelerated aging stress such as 0.95 $V_{1㎃}$15$0^{\circ}C$/12 h)

DC Accelerated Aging Characteristics of $ZnO-Pr_{6}O_{11}$ Based Varistor Ceramics ($ZnO-Pr_{6}O_{11}$계 바리스터 세라믹스의 직류가속열화 특성)

  • Kim, Hyang-Suk;Nahm, Choon-Woo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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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, $0.95 V_{1mA}/150^{\circ}C/24h$.

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DC Accelerated Aging Characteristics of $Pr_{6}O_{11}$-Based ZnO Varistors with CoO Content (CoO 첨가량에 따른 $Pr_{6}O_{11}$계 ZnO 바리스터의 DC 가속열화특성)

  • Kim, Hyang-Suk;Jung, Young-Chul;Nahm, Choon-Woo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.467-471
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    • 2001
  • DC accelerated aging characteristics of $Pr_{6}O_{11}$-based ZnO varistors, which are composed of $ZnO+Pr_{6}O_{11}+CoO+Cr_{2}O_{3}+Dy_{2}O_{3}$ ceramics were investigated with CoO content in the range of 0.5 - 5.0 mol%. The varistors doped with 1.0 mol% revealing maximum value(66.61) in the nonlinear exponent exhibited excellent stability, in which the variation rates of the varistor voltage, the nonlinear exponent and leakage current are -1.93%, -10.48%, and +288.79%, respectively, under DC accelerated aging stress, such as $(0.85V_{lmA}/115^{\circ}C/24h)+(0.90V_{lmA}120^{\circ}C/24h)+(0.95V_{lmA}/125^{\circ}C/24h)+(0.95V_{lmA}/150^{\circ}C/24h)$. Next the varistors doped with 2.0 mol% exhibiting the nonlinear exponent of 47.39 showed high stability.

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DC Accelerated Aging Characteristics of $Pr_{8}O_{11}$-Based ZnO Varistors with CoO Content (CoO 첨가량에 따른 $Pr_{8}O_{11}$계 ZnO 바리스터의 DC 가속열화특성)

  • 김향숙;정영철;남춘우
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.467-471
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    • 2001
  • DC accelerated aging characteristics of Pr$_{6}$O$_{11}$-based ZnO varistors, which are composed of ZnO+Pr$_{6}$O$_{11}$+CoO+Cr$_2$O$_3$+Dy$_2$O$_3$ ceramics were investigated with CoO content in the range of 0.5~5.0 mol%. The varistors doped with 1.0 mol% revealing maximum value(66.61) in the nonlinear exponent exhibited excellent stability, in which the variation rates of the varistor voltage, the nonlinear exponent and leakage current are -1.93%, -10.48%, and 288.79%, respectively, under DC accelerated aging stress, such as (0.85 V$_{1mA}$/115$^{\circ}C$/24h)+(0.90 V$_{1mA}$/12$0^{\circ}C$/24h)+(0.95 V$_{1mA}$/1$25^{\circ}C$/24h)+(0.95 V$_{1mA}$/15$0^{\circ}C$/24h). Next the varistors doped with 2.0 mol% exhibiting the nonlinear exponent of 47.39 showed high stability,ity,ability,ity,

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Microstructure, Electrical Properties, and Accelerated Aging Behavior of Er-Added ZPCC-YE Varistors

  • Nahm, Choon-Woo;Park, Jong-Hyuk
    • Transactions on Electrical and Electronic Materials
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    • v.11 no.5
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    • pp.216-221
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    • 2010
  • The microstructure, electrical properties, and DC-accelerated aging behavior of the Zn-Pr-Co-Cr-Y-Er (ZPCC-YE) varistors were investigated for different amounts of erbium oxide ($Er_2O_3$). The microstructure consisted of zinc oxide grain and an intergranular layer ($Pr_6O_{11}$, $Y_2O_3$, and $Er_2O_3$-rich phase) as a secondary phase. The increase of $Er_2O_3$ amount decreased the average grain size and increased the sintered density. As the $Er_2O_3$ amount increased, the breakdown field increased from 5094 V/cm to 6966 V/cm and the nonlinear coefficient increased from 27.8 to 45.1. The ZPCC-YE varistors added with 0.5 to 1.0 mol% $Er_2O_3$ are appropriate for high voltage, with high nonlinearity and stability against DC-accelerated aging stress.

DC Accelerated Aging Characteristics of Dy2O3-Doped ZPCCD-Based Varistors (Dy2O3가 첨가된 ZPCCD계 바리스터의 DC 가속열화 특성)

  • 남춘우;박종아;김명준
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.16 no.12
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    • pp.1071-1076
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    • 2003
  • The nonlinear properties and their stability of ZPCCD- based varistors, which are composed of ZnO P $r_{6}$ $O_{ll}$ - CoO-C $r_2$ $O_3$-D $y_2$ $O_3$-based ceramics, were investigated in the D $y_2$ $O_3$ content range of 0.0∼2.0 mol%. The incorporation of D $y_2$ $O_3$ greatly affected the nonlinear properties and the best nonlinearity was obtained from 0.5 mol% D $y_2$ $O_3$ with nonlinear exponent of 66.6 and leakage current of 1.2 $\mu$A. Further addition of D $y_2$ $O_3$ deteriorated the nonlinear properties. In stability against DC accelerated aging stress state: 0.95 $V_{1mA}$/15$0^{\circ}C$/24 h, the 0.5 mol% D $y_2$ $O_3$-doped varistor exhibited the highest stability, in which the variation rate of varistor voltage and nonlinear exponent are -1.9% and 10.5%, respectively. The remainder varistors resulted in thermal runaway due to low density of ceramics.s.s.

Electrical Properties and Stability of La2O3 Doped ZnO-Pr6O11-Based Varistor Ceramics (La2O3 Doped ZnO-Pr6O11계 바리스터 세라믹스의 전기적 성질 및 안정성)

  • Nahm, Choon-Woo
    • Journal of the Korean Ceramic Society
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    • v.43 no.6
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    • pp.383-388
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    • 2006
  • The varistor properties and DC accelerated aging characteristics of $ZnO-Pr_{6}O_{11}-CoO-Cr_{2}O_{3}$-based varistors were investigated at different $La_{2}O_3$ contents in the range of $0{\sim}2.0mol%$. The varistors doped with 0.5 mol% $La_{2}O_3$ exhibited good nonlinearity, with 81.6 in nonlinear coefficient. Increasing the $La_{2}O_3$ content further to 2.0 mol% caused the sintered density to increase, and the breakdown voltage and nonlinearity to decrease abruptly. The varistors with 0.5 mol% $La_{2}O_3$ exhibited the high electrical stability, with -1.14% in variation rate of breakdown voltage, -3.7% in variation rate of nonlinear coefficient, and +100% in variation rate of leakage current for specified DC accelerated aging stress condition (95% of breakdown voltage/$150^{\circ}C$/24 h).

DC Accelerated Aging Characteristics of Zn-Pr-Co-Cr-La Oxides-Based Varistors with Sintering Temperature (소결온도에 따른 Zn-Pr-Co-Cr-La 산화물계 바리스터의 DC 가속열화 특성)

  • Kim, Myung-Jun;Yoo, Dae-Hoon;Park, Jong-Ah;Nahm, Choon-Woo
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.383-386
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    • 2004
  • DC accelerated aging characteristics of Zn-Pr-Co-Cr-La oxides-based varistors were investigated with various sintering temperatures. The varistors sintered at $1240^{\circ}C$ exhibited the highest nonlinearity, with a nonlinear exponent of 79.3 and a leakage current of $0.3\;{\mu}A$, whereas completely degraded because of thermal runaway owing to low sintered density. The varistors sintered at $1250^{\circ}C$ exhibited not only a high nonlinearity with the nonlinear exponent 61.4 and the leakage current 0.7 ${\mu}A$, but also a high stability with the variation rates of varistor voltage and nonlinear exponent are -1.01% and -10.67%, respectively, under DC stress condition such as $(0.85\;V_{1mA}/115^{\circ}C/24\;h)+(0.90\;V_{1mA}/120^{\circ}C/24\;h)+(0.95\;V_{1mA}/125^{\circ}C/24\;h)+(0.95\;V_{1mA}/150^{\circ}C/24\;h)$.

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