소결 조건 변화에 따른 직류 피뢰기용 ZnO 바리스터의 미세구조 및 전기적 성질에 관한 연구

김석수,최익순,박태곤,조이곤,박춘현,Kim, Seok-Sou,Choi, Ike-Sun,Park, Tae-Gon,Cho, I-Gon,Park, Choon-Hyun 한국전기전자재료학회 2004 전기전자재료학회논문지 Vol.17 No.6

The microstructure and electrical characteristics of A ∼ C's ZnO varistors fabricated according to variable sintering condition, which sintering temperature was 1130 $^{\circ}C$ and speeds of pusher were A: 2 mm/min, B: 4 mm/min, C: 6 mm/min, respectively, were investigated. The experimental results obtained from this study were summarized as follows: The sintering density of A ∼C's ZnO varistors sintered at 1130 $^{\circ}C$ were decreased by sintering keep time to shorten, such as A: 9hour, B: 4.5hour and C: 3hour. A's ZnO varistor exhibited good densification nearly 98 % of theory density. In the microstructure, A∼C's ZnO varistors fabricated variable sintering condition was consisted of ZnO grain(ZnO), spinel phase(Z $n_{2.33}$S $b_{0.67}$ $O_4$), Bi-rich phasc(B $i_2$ $O_3$), wholly. Varistor voltage of A∼C's ZnO varistors sintered at 1130 $^{\circ}C$ increased in order A <B <C's ZnO varistors. C's ZnO varistor exhibited good characteristics that nonlinear exponent was 31.70. Leakage current of A ∼ C's ZnO varistors exhibited below 2 ㎃ at rated voltage. Lightning impulse residual voltage of A's ZnO varistor suited standard characteristics, which was 3.85kV at 2.5kA, 4.4 kV at 5kA and 5.16 kV at 10 kA. After continuous lightning impulse current test of A's ZnO varistor exhibited good discharge characteristics which ZnO varistor reveals no evidence of puncture, flashover, cracking in visual examination. After high current impulse test of A's ZnO varistor exhibited good discharge characteristics, which variation rate of residual voltage was 0.4 % before and after test, and revealed no evidence. evidence.

ZnO 나노분말로 제조한 Bi계 바리스터의 써지내량 특성

왕민성,박춘배,Wang, Min-Sung,Park, Choon-Bae 한국전기전자재료학회 2006 전기전자재료학회논문지 Vol.19 No.9

Bi-based nano-varistors and micro-varistors fabricated with each ZnO nano-powder and micro-powder were studied about characteristics on the surge capability in this study. ZnO nano-varistors were sintered in air at $1050^{\circ}C$ for 2 hr. The voltage-current and residual voltage properties of ZnO nano-varistor were compared with their of ZnO micrio-varistor. As a result of these properties, our ZnO nano-varistor has about 3 times at operating voltage as compared with conventional ZnO varistor fabricated with micro-powder and the residual voltage was 8.06 kV at nominal discharge current 101kA in the lighting impulse current test. And then the residual voltage rate 1.72 of our nano-varistor has had better performance than the 1.79 of micro-varistor because ZnO nano-varistor has shown much quick response property because of increasing effective cross-section area. Also, to analysis surge capability took thermal images for pyrexia temperature distribution with each of the varistors after operating varistors. Nano-varistor doesn't have shown local overheating and can confirm accurate temperature grade on the surface of its.

3층으로 적층된 ZnO 바리스터의 열분포 해석

장경욱 ( Kyung-uk Jang ) 한국전기전자재료학회 2023 전기전자재료학회논문지 Vol.36 No.4

Recently, as power and electronic devices have increased in frequency and capacity, it has become a major concern to protect electronic circuits and electronic components used in these devices from abnormal voltages such as various surges and pulse noise. To respond to variously rated voltages applied to power electronic devices, the rated voltages of various varistors can be obtained by controlling the size of internal particles of the varistor or controlling the number of layers of the varistor. During bonding, the problem of unbalanced thermal runaway occurring between the electrode and the varistor interface causes degradation of the varistor and shortens its life of the varistor. In this study, to solve the problem of unbalanced heat distribution of stacked varistors to adjust the operating voltage, the contents of the ZnO-based varistor composition were 96 wt% ZnO, 1 mol% Sb₂O₃, 1 mol% Bi₂O₃, 0.5 mol% CoO, 0.5 mol% MnO, and 1 mol% TiO₂. A multi-layered ZnO varistor was modeled by bonding a single varistor with a composition in three layers according to the operating voltage. The thermal distribution of the triple-layered ZnO varistor was analyzed for the thermal runaway phenomenon that occurred during varistor operation using the finite element method according to Comsol 5.2.

유한요소법에 의한 ZnO 바리스터 동작 시 발생되는 열폭주 현상 해석

장경욱 한국전기전자재료학회 2022 전기전자재료학회논문지 Vol.35 No.4

Since the ZnO varistor is a semiconductor device, the internal thermal distribution during the varistor operation is recognized as an important factor in the performance and deterioration of the varistor. For an optimal varistor structure design, the thermal runaway phenomenon during the varistor operation was interpreted using the Comsol 5.2 analysis program by a finite element analysis. The maximum temperature of the center measured in the cross section of the ZnO varistor was confirmed to increase as the temperature moved from the lower electrode to the center towards the upper electrode up to 572.6 K. The electrodes are thinned so that the influence of the Schottky barrier is not great. The heat gradient balance is determined to be improved when the electrode of the hybrid form is introduced. The thickness, density, pore distribution, impurity uniformity, and particle size of the ZnO varistor are required, and it is determined that the pyrolysis gradient will be improved regardless of the electrode thickness. When these results are applied to design the ZnO varistor, the optimal structure of the ZnO varistor can be obtained.

8/20 [μs] 임펄스전류의 인가횟수와 크기가 ZnO바리스터의 수명에 미치는 영향

이복희,이봉,Lee, Bok-Hee,Li, Feng 한국조명전기설비학회 2007 조명·전기설비학회논문지 Vol.21 No.1

This paper presents the effects of the injected number and amplitude of impulse current on the service life of ZnO varistors for low voltages. To analyze the effects of lightning impulse currents on the performance of ZnO varistors, the measurements of resistive leakage current and power dissipation at the power frequency ac voltage before and after the injections of the $8/20[{\mu}s]$ impulse currents were made. As a consequence, the duration and amplitude of resistive leakage current flowing through ZnO varistor were increased with increasing the number of injections of the $8/20[{\mu}s]$ impulse currents. It is desirable that the service life of ZnO varistors should be evaluated as a function of the number and amplitude of lightning impulse current. 본 논문에서는 임펄스전류의 크기와 인가횟수가 ZnO바리스터의 수명에 미치는 영향에 관한 것으로 뇌임펄스전류가 ZnO바리스터의 성능에 미치는 영향을 분석하기 위하여 $8/20[{\mu}s]$임펄스전류가 인가되기 전후 ZnO바리스터의 상용주파수 교류전압에 대한 저항성 누설전류와 손실전력을 측정하였다. 그 결과 $8/20[{\mu}s]$임펄스전류의 인가횟수가 증가함에 파라 ZnO바리스터에 흐르는 저항성 누설전류는 증가하고 통과시간은 길어졌다. ZnO바리스터의 수명은 뇌임펄스전류의 크기와 인가횟수에 대해서 평가하는 것이 바람직하다.

The Effect of Chrome Oxide on the Threshold Voltage of ZnO Varistor

추순남 경원전문대학 1995 論文集 Vol.17 No.2

ZnO바리스터의 문턱전압(절연파괴 개시전압)은 바리스터의 규정전압을 평가하는데 있어서 매우 중요한 요소이다. Bi산화물를 기본조성으로 한 ZnO바리스터의 문턱전압에 미치는 크롬산화물의 영향에 대하여 조사하였다. 전자주사현미경의 관찰로부터 크롬산화물에 따른 결정립과 결정입계의 변화를 관찰하였다. 문턱전압은 입계층 상태와 입자크기에 의존하게 됨을 알았다. ZnO 바리스터의 정전용량과 입자크기는 크롬산화물의 증가와 함께 감소 되었다. 그리고 겉보기 문턱전압의 증가는 ZnO 입자내부에 존재하는 공핍층 도너밀도의 감소특성에 기인되었다. 이들의 결과들은 C-V특성, 절연파괴전압 그리고 미세구조사진으로부터 얻어졌다. Threshold voltage ZnO varistor, critical point of breakdown voltage, is important electrical parameter that is necessary for quantitative evaluation of the rated varistor voltage. The effect of Cr₂O₃ additive on the threshold voltage characteristics of Bi-based ZnO ceramic varistor was studies. From the observation of Scanning Electron Microscopy, grain size and grain boundary according to Cr₂O₃ content was investigated. The thresh-old voltage of the ZnO ceramics was dominated by grain boundary interface states and grain size. The capacitance and grain size decreased with increasing Cr₂O₃ content, It is found that the increases in the apparent threshold voltage is associated with the lowered donor concentration in depletion region of ZnO grain. These result are obtained by measuring C-V characteristics, breakdown voltage at the current density 1O A/㎠ and micro-structure of ZnO ceramics.

ZnO-Zn₂BiVO₆-Mn₃O₄ 바리스터의 미세구조와 전기적 특성

홍연우,하만진,백종후,조정호,정영훈,윤지선,Hong, Youn-Woo,Ha, Man-Jin,Paik, Jong-Hoo,Cho, Jeong-Ho,Jeong, Young-Hun,Yun, Ji-Sun 한국전기전자재료학회 2018 전기전자재료학회논문지 Vol.31 No.5

This study introduces a new investigation report on the microstructural and electrical property changes of $ZnO-Zn_2BiVO_6-Mn_3O_4$ (ZZMn), where 0.33 mol% of $Mn_3O_4$ and 0.5 mol% of $Zn_2BiVO_6$ were added to ZnO (99.17 mol%) as liquid phase sintering aids. $Zn_2BiVO_6$ contributes to the decrease of sintering temperatures by up to $800^{\circ}C$, and segregates its particles at the grain boundary, while $Mn_3O_4$ enhances ${\alpha}$, the nonlinear coefficient, of varistor properties up to ${\alpha}=62$. In comparison, when the sintering temperature is increased from $800^{\circ}C$ to $1,000^{\circ}C$, the resistivity of ZnO grains decreases from $0.34{\Omega}cm$ to $0.16{\Omega}cm$, and the varistor property degrades. Oxygen vacancy ($V_o^{\bullet}$) (P1, 0.33~0.36 eV) is formed as a dominant defect. Two different kinds of grain boundary activation energies of P2 (0.51~0.70 eV) and P3 (0.70~0.93 eV) are formed according to different sintering temperatures, which are tentatively attributed to be $ZnO/Zn_2BiVO_6$-rich interface and ZnO/ZnO interface, respectively. Accordingly, this study introduces a progressive method of manufacturing ZnO chip varistors by way of sintering ZZMn-based varistor under $900^{\circ}C$. However, to procure a higher reliability, an in-depth study on the multi-component varistors with double-layer grain boundaries should be executed.

8/20 [㎲]임펄스전류의 인가횟수와 크기가 ZnO바리스터의 수명에 미치는 영향

이복희(Bok-Hee Lee),이봉(Feng Li) 한국조명·전기설비학회 2007 조명·전기설비학회논문지 Vol.21 No.1

본 논문에서는 임펄스전류의 크기와 인가횟수가 ZnO바리스터의 수명에 미치는 영향에 관한 것으로 뇌임펄스전류가 ZnO바리스터의 성능에 미치는 영향을 분석하기 위하여 8/20 [㎲]임펄스전류가 인가되기 전후 ZnO바리스터의 상용주파수 교류전압에 대한 저항성 누설전류와 손실전력을 측정하였다. 그 결과 8/20 [㎲]임펄스전류의 인가횟수가 증가함에 따라 ZnO바리스터에 흐르는 저항성 누설전류는 증가하고 통과시간은 길어졌다. ZnO바리스터의 수명은 뇌임펄스전류의 크기와 인가횟수에 대해서 평가하는 것이 바람직하다. This paper presents the effects of the injected number and amplitude of impulse current on the service life of ZnO varistors for low voltages. To analyze the effects of lightning impulse currents on the performance of ZnO varistors, the measurements of resistive leakage current and power dissipation at the power frequency ac voltage before and after the injections of the 8/20 [㎲] impulse currents were made. As a consequence, the duration and amplitude of resistive leakage current flowing through ZnO varistor were increased with increasing the number of injections of the 8/20 [㎲] impulse currents. It is desirable that the service life of ZnO varistors should be evaluated as a function of the number and amplitude of lightning impulse current.

ZnO계 바리스터의 입계포획준위

김명철,박순자,Kim, Myung-Chul,Park, Soon-Ja 한국재료학회 1992 한국재료학회지 Vol.2 No.1

등온용량과도분광법(Isothermal Capacitance Transient spectroscopy)을 이용하여 ZnO 바리스터의 포획준위를 결정하였다. 여기서 등온용량과도분광기는 YHP 4192A 임피던스 Analyzer와 데이터해석을 위한 개인용 컴퓨터로 구성된다. 이 실험에서 우리는 $ZnO-Bi_2O_3$에 MnO 및 CoO를 첨가한계에서 $-40^{\circ}C~60^{\circ}C$ 온도범위에서 0.28, 0.48, 0.50, 0.94eV 등의 입계포획준위가 존재함을 볼 수 있었다. 또한, $ZnO-Bi_2O_3$계는 CoO를 첨가하면 hole에 의한 emission특성을 나타내고, MnO를 첨가하면 전자에 의한 emission특성을 나타냄을 알 수 있었다. 그리고 비 직선저항계수 $\alpha$는 도너농도의 감소에 직접적으로 비례하였으나, 포획준위의 밀도와는 별다른 비례관계를 발견할 수 없었다. 결론적으로 $ZnO-Bi_2O_3-MnO$계에 CoO를 첨가함에 따라 $\alpha$값이 증가하는 한편, 포획준위밀도는 CoO의 첨가로 감소함을 알 수 있었다. The trap levels of ZnO-based varistor are obtained by Isothermal Capacitance Transient Spectroscopy method. Here ICTS measuring system consists of YHP 4192A Impedance Analyzer and a personal computer for the data acquisition. Between $-40^{\circ}C$ and $60^{\circ}C$, the grain boundary trap levels of 0.48 and 0.94eV were detected for $ZnO-Bi_2O_3-MnO$ system. The hole omission spectra are observed in the case of the addition of CoO into the $ZnO-Bi_2O_3$ system, while the electron emission spectra are detected in the case of the addition of MnO. The nonlinear resistance coefficient $\alpha$ increases with the decrease of the dormer concentration. Finally, the trap level density of $ZnO-Bi_2O_3-MnO$ system is found to decrease with the amount of CoO, while $\alpha$ is found to increase with the amount of CoO.

ZnO-Zn₂BiVO₆-Co₃O₄-Cr₂O₃-CaCO₃ 바리스터 내의 결정결함과 입계특성

홍연우,하만진,Hong, Youn-Woo,Ha, Man-Jin 한국전기전자재료학회 2019 전기전자재료학회논문지 Vol.32 No.4

In this study, we investigated the crystal defects and grain boundary properties in a ZZCCC ($ZnO-Zn_2BiVO_6-Co_3O_4-Cr_2O_3-CaCO_3$) varistor, with the liquid-phase sintering aid $Zn_2BiVO_6$ developed by our laboratory. The ZZCCC varistor sintered at $1,200^{\circ}C$ exhibited excellent nonlinear current-voltage characteristics (${\alpha}=63$), with oxygen vacancy ($V_o^*$ ; 0.35 eV) as a main defect, and an apparent activation energy of 1.1 eV with an electrically single grain boundary. Therefore, among the various additives to improve the electrical properties of ZnO varistors, if $Zn_2BiVO_6$ is used as a liquid phase sintering aid, it will be ideal to use Co for the oxygen vacancy and Ca for the electrically single grain boundary. This will allow the good properties of ZnO varistors to be maintained up to high sintering temperatures.