Performance Of ZnO Varistors Research Articles

Effect of the sintering temperature on the electrical properties of Y–Al‐doped ZnO varistors

AbstractTo investigate the relationship between the electrical properties of Y–Al doped ZnO varistors and sintering temperature, in this study, we measured the voltage–current characteristics and electrical performance parameters of samples sintered at –. Scanning electron microscopy observations revealed that as the sintering temperature increased, the grain size grew significantly, leading to a reduction in voltage gradient. Through characteristic testing, X‐ray diffraction and energy dispersive X‐ray spectroscopy analysis, it was found that the increase in sintering temperature promoted the formation of interface negative charge and defect reactions by , increasing and ; tends to aggregate in the grain area, further increasing ; the volatilization of gradually increases, causing a decrease in ; the first increases and then decreases with the changes in and , resulting in a U‐shaped variation characteristic of the nonlinear coefficient and leakage current density. At a sintering temperature of , the performance of ZnO varistors is optimal.

Characterization and Performance Evaluation of Zinc Oxide Varistor Blocks Processed by Latex Binders

The processing of ZnO varistor has a long route with numerous contributing variables. The binder plays an important role in the fabrication of this electro-ceramic device. Higher density and strength of a green body are critical not only for handling at its green state but also to avoid the causes of flaw formation during sintering. Use of appropriate binder can lead to improved characteristics of powder, which will reduce density gradient in the green body during compaction. Enhanced green properties can consequently lead to higher fired strength of the varistor discs. The binder system is anticipated to have an influence on the grain growth and microstructure which in turn affect the electrical performance parameters of the discs such as I–V characteristics, watt-loss behavior, and energy absorption capability, etc. To investigate this phenomenon, several commercial latex binders and their blends have been studied and compared with the conventional plasticized polyvinyl alcohol. A positive effect was observed in the context of physical properties and electrical performance of ZnO varistors. Factorial analysis has revealed that the two input parameters (binder content and solid concentration) influence the electrical properties such as electric field intensity, non-linear co-efficient, energy absorption capability, and watt-loss of ZnO varistor.

Relations between the Morphology of ZnO Powders and the Electrical Performance of ZnO Varistors

Because of their unusual properties – non-ohmic behavior and the ability to absorb a lot of energy – metal-oxide varistors are widely used for the protection of electrical and electronic devices against over-voltages. ZnO ceramics have varistor properties because of their metal-oxide additives and the microstructures developed during sintering. The value of the varistor voltage depends largely on the number of conducting ZnO grains between the electrodes; this can be set by controlling the thickness of the device or the size of the grains. The desired grain size can be achieved by altering the composition of the metal-oxide additives and the sintering conditions. In this work the grain growth was controlled by combining two ZnO powders of differing sinterability in the starting material. Also, the use of BaBiO2.77 as a precursor for Bi2O3 is an innovation in varistor technology that makes it possible to reduce the amount of added metal oxides. As a result, a variety of varistors with good varistor properties and a wide range of working parameters were produced.

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

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.