http://chineseinput.net/에서 pinyin(병음)방식으로 중국어를 변환할 수 있습니다.
변환된 중국어를 복사하여 사용하시면 됩니다.
ZnO-Pr_6O_11-CoO-Y₂O₃계 세라믹스 바리스터 특성
남춘우,윤한수,류정선 동의대학교 산업기술개발연구소 2001 産業技術硏究誌 Vol.15 No.-
Varistor characteristics of ZnO-Pr6O11-CoO-Y2O3 based ceramics doped with Y2O3 in the range of 0.0 ~ 4.0 mol%, sintered at 1350℃ for 1h were investigated. The average grain size of ZnO-Pr6O11-CoO-Y2O3 based ceramics decresaed in the range of 18.36 ∼ 4.38 μm with increasing Y2O3 additive content. The ceramics without Y2O3 exhibited very low nonlinearity, which the nonlinear exponent is 2.08 and the leakage current is 133.86 μA. However, the ceramics with Y2O3 exhibited in the range of 22.64 ∼ 30.08 in the nonlinear exponent and 13.88 ~ 28.49 μA in the leakage current. The ceramics with 2.0 mol% Y2O3 exhibited the good characteristics, which the nonlinear exponent is 30.08 and the leakage current is 18.63 μA. With increasing Y2O3 content, the density of interface states and the donor concentration decreased in the range of (6.30 ∼ 2.48) × 1012/cm2 and (14.63 ∼ 0.61) × 1018/cm3, respectively. It is estimated ZnO-Pr6O11-CoO- Y2O3 based ceramics, which Y2O3 will be used as additive improving a nonlinear exponent to develop a good ZnO varistor.
Microstructure, Electrical Properties, and Accelerated Aging Behavior of Er-Added ZPCC-YE Varistors
Nahm, Choon-Woo,Park, Jong-Hyuk The Korean Institute of Electrical and Electronic 2010 Transactions on Electrical and Electronic Material Vol.11 No.5
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.
Electrical Properties of PCCYA-doped ZnO-based Varistors
Nahm, Choon-Woo The Korean Institute of Electrical and Electronic 2008 Transactions on Electrical and Electronic Material Vol.9 No.3
The microstructure, voltage-current, and capacitance-voltage relations ofP CCYA doped ZnO-based varistors were investigated for different amounts of $Al_2O_3$. As the $Al_2O_3$ amount increased, the average grain size (d) increased from d=4.3 to $d=5.5{\mu}m$ and the sintered density $({\rho})$ increased from ${\rho}=5.63$ to ${\rho}=5.67g/cm^3$. As the $Al_2O_3$ amount increased, the breakdown voltage $(V_B)$ increased from $V_B=633$ to $V_B=71$ V/mm and the non-ohmic coefficient $({\alpha})$ increased from ${\alpha}=47$ to ${\alpha}=4$. $Al_2O_3$ served as a donor due to the donor density $(N_d)$, which increases in the range of $N_d=0.77-1.85{\times}10^{18}/cm^3$ with increasing amount of $Al_2O_3$.
Nahm, Choon-Woo The Korean Institute of Electrical and Electronic 2009 Transactions on Electrical and Electronic Material Vol.10 No.3
The microstructure, voltage-current, capacitance-voltage, and dielectric characteristics of CCT doped Zn/Pr-based varistors were investigated at different sintering temperatures. As the sintering temperature increased, the average grain size increased from 4.3 to 5.1 ${\mu}m$ and the sintered density was saturated at 5.81 g $cm^{-3}$. As the sintering temperature increased, the breakdown field decreased from 7,532 to 5,882 V $cm^{-1}$ and the nonlinear coefficient decreased from 46 to 34. As the sintering temperature increased, the donor density, density of interface states, and barrier height decreased in the range of (9.06-7.24)${\times}10^{17}\;cm^{-3}$, (3.05-2.56)${\times}10^{12}\;cm^{-2}$, and 1.1-0.95 eV, respectively. The dielectric constant exhibited relatively low value in the range of 529.1-610.3, whereas the $tan{\delta}$ exhibited a high value in the range of 0.0910-0.1053.
Nahm, Choon-Woo The Korean Institute of Electrical and Electronic 2015 Transactions on Electrical and Electronic Material Vol.16 No.6
V<sub>2</sub>O<sub>5</sub>/Mn<sub>3</sub>O<sub>4</sub>/Nb<sub>2</sub>O<sub>5</sub> codoped zinc oxide varistor ceramics were sintered at a temperature range as low as 875~950℃. The voltage clamping characteristics of V<sub>2</sub>O<sub>5</sub>/Mn<sub>3</sub>O<sub>4</sub>/Nb<sub>2</sub>O<sub>5</sub> codoped zinc oxide varistor ceramics were investigated at a pulse current range of 1~50 A. The sintering temperature had a significant effect on clamp voltage ratio, which exhibits surge protection capabilities. The varistor ceramics sintered at 875℃ exhibited the best clamping characteristics, in which the clamp voltage ratio was 2.69 at a pulse current of 50 A. The varistor ceramics sintered at 900℃ exhibited the highest electrical stability, where = 3,824 V/cm (initial 3,909 V/cm), and E<sub>1 mA/cm<sup>2</sup></sub> = 27 (initial 39) after application of a pulse current of 100 A.
Degradation Characteristics of Pr/Co/Cr/Er Co-doped Zinc Oxide Varistors by Impulse Current Stress
Nahm, Choon-Woo The Korean Institute of Electrical and Electronic 2014 Transactions on Electrical and Electronic Material Vol.15 No.6
In light of the sure protection function, the most important factors of a varistor are the clamping voltage ratio and degradation characteristics. The degradation characteristics of Pr/Co/Cr/Er co-doped zinc oxide varistors were investigated by impulse currents (0.4~2.1 kA) stress for the specified content of $Er_2O_3$ (0.5 and 2.0 mol%). The varistor doped with 2.0 mol% $Er_2O_3$ exhibited the best clamp characteristics, with the clamp voltage ratio (K) in the range of K = 1.63~1.88 at the impulse currents of 5-50 A. However, the varistor doped with 0.5 mol% exhibited excellent electrical stability, with variation rates for the breakdown field, for the nonlinear coefficient, and for the leakage current density of -6.9%, -12.6%, and -14.3%, respectively, after application of an impulse current of 2.1 kA. In contrast, the varistor doped with 2.0 mol% was destroyed after application of an impulse current of 1.2 kA.
Nahm, Choon-Woo The Korean Institute of Electrical and Electronic 2014 Transactions on Electrical and Electronic Material Vol.15 No.5
The effects of additives (Nb, Bi and Cr) on the microstructure, varistor properties, and aging behavior of V/Mn/Co/ La/Dy co-doped zinc oxide ceramics were systematically investigated. An analysis of the microstructure showed that all of the ceramics that were modified with various additives were composed of zinc oxide grain as the main phase, and secondary phases such as $Zn_3(VO_4)_2$, $ZnV_2O_4$, and $DyVO_4$. The $Bi_2O_3$-modified samples exhibited the lowest density, the $Nb_2O_5$-modified sample exhibited the largest average grain size, and the $Cr_2O_3$-modified samples exhibited the highest breakdown field. All additives improved the non-ohmic coefficient (${\alpha}$) by either a small or a large margin, and in particular an $Nb_2O_5$ additive noticeably increased the non-ohmic coefficient to be as large as 36. The $Bi_2O_3$-modified samples exhibited the highest stability with variation rates for the breakdown field and for the non-ohmic coefficient (${\alpha}$) of -1.2% and -26.3%, respectively, after application of a DC accelerated aging stress of 0.85 EB/$85^{\circ}C$/24 h.
Microstructure and Varistor Properties of ZVMND Ceramics with Sintering Temperature
Nahm, Choon-Woo The Korean Institute of Electrical and Electronic 2015 Transactions on Electrical and Electronic Material Vol.16 No.4
The sintering effect on the microstructure, electrical properties, and dielectric characteristics of ZnO-V<sub>2</sub>O<sub>5</sub>-MnO<sub>2</sub>-Nb<sub>2</sub>O<sub>5</sub>-Dy<sub>2</sub>O<sub>3</sub>-based ceramics was investigated. With the increase of sintering temperature from 875 to 950℃, the density of the sintered pellets decreased from 5.57 to 5.45 g/cm<sup>3</sup> and the average grain size increased from 4.3 to 10.9 μm. The breakdown field decreased noticeably from 6,095 to 996 V/cm with the increase of sintering temperature. The varistor ceramics sintered at 900℃ exhibited the best nonlinear properties: 39.2 in the nonlinear coefficient and 0.24 mA/cm<sup>2</sup> in the leakage current density. The dielectric constant increased sharply from 658.6 to 2,928.8 with the increase of sintering temperature. On the whole, the dissipation factor exhibited a fluctuation with the increase of the sintering temperature, and a minimum value of 0.284 at 900℃.
Nahm, Choon-Woo The Korean Institute of Electrical and Electronic 2006 Transactions on Electrical and Electronic Material Vol.7 No.3
The microstructure and electrical properties of the varistors, which are composed of $ZnO-Pr_6O_{11}-CoO-Cr_2O_3-La_2O_3-based$ ceramics, were investigated for different $La_2O_3$ contents. The increase of $La_2O_3$ content led to more densified ceramics, whereas abruptly decreased the nonlinear properties by incorporating beyond 1.0 mol%. The highest nonlinearity was obtained from 0.5 mol% $La_2O_3$, with the nonlinear coefficient of 81.6 and the leakage current of $0.2{\mu}A$. The increase of sintering time and temperature greatly decreased the nonlinear properties. As the $La_2O_3$ content increased, the donor density increased from $0.64\times10^{18}/cm^3\;to\;16.89\times10^{18}/cm^3$ and the barrier height greatly decreased with increasing $La_2O_3$ content, reaching a maximum (1.47 eV) in 0.5 mol% $La_2O_3$.
Influence of Dy Doping on Electrical Properties and dc Aging Behaviors of Zn-Pr-Co-Cr System
Nahm, Choon-Woo The Korean Institute of Electrical and Electronic 2007 Transactions on Electrical and Electronic Material Vol.8 No.6
The electrical properties and dc aging behavior for specified stress state of system, which is composed of quaternary Zn-Pr-Co-Cr, were investigated for different $Dy_2O_3$ addition doping level. As $Dy_2O_3$ doping level increased, the density decreased in the range of 5.51-4.90 $g/cm^3$, reaching maximum at 0.5 mol% and the average ZnO grain size decreased in the range of 17.7-6.0 ${\mu}m$. The incorporation of $Dy_2O_3$ significantly improved the non-ohmic properties, above 30 in non-ohmic coefficient, compared with that of undoped samples. The samples with the best performance of non-ohmic properties were obtained for $Dy_2O_3$ doping level of 1.0 mol%, with 49 in non-ohmic coefficient and 2.6 ${\mu}A/cm^2$ in leakage current. The samples with the highest stability were obtained for $Dy_2O_3$ doping level of 0.5 mol%.