scholarly journals DC Aging Mechanism of Co2O3-Doped ZnO Varistors

Energies ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 4011
Author(s):  
Xia Zhao ◽  
Haibin Shen ◽  
Men Guo ◽  
Ziming He ◽  
Yupeng Li ◽  
...  
Keyword(s):  
Breakdown Field ◽  
Electrical Parameters ◽  
Positive Direction ◽  
Negative Direction ◽  
Dielectric Relaxations ◽  
Oxygen Ion ◽  
Zinc Interstitial ◽  
Zno Varistors ◽  
Dc Bias ◽  
Doped Zno

Lowered power loss and asymmetrically electrical parameters are reported in the DC aging of Co2O3-doped ZnO varistors in this paper. Based on the frequency domain dielectric responses of the pristine and degraded samples, the present study explores the roles of point defects in the aging process via dielectric relaxations and their parameters. It is found that breakdown field increased more in the positive direction than the negative direction. Nonlinearity increased in the positive direction, whereas it decreased in the negative direction, and leakage current density increased more in the negative direction than the positive direction. Given the lowest migration energy of Zinc interstitial (Zni, 0.57 eV) and high oxygen ion conductivity in Bi2O3-rich phase, it is speculated that Zni and adsorbed oxygen (Oad) migrate under DC bias, and then change the defect structure and the double Schottky barrier (DSB) at grain boundaries. As a result, the forward-biased barrier height gradually decreases more than the reverse-biased one.

Analyses of defect distributions in ZnO varistors based on the Jonscher’s universal power law and the Dissado–Hill model

2021 ◽  
Vol 55 (13) ◽  
pp. 135106
Author(s):  
Xia Zhao ◽  
Men Guo ◽  
Yuandong Wen ◽  
Weidong Shi ◽  
Boyu Zhang ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Power Law ◽  
Current Density ◽  
Nonlinear Coefficient ◽  
Breakdown Field ◽  
Hill Model ◽  
X Ray ◽  
Universal Power Law ◽  
Zno Varistors ◽  
Doped Zno

Abstract The defect distributions in ZnO varistors mixed with Bi2O3, NiO, MnCO3, Co2O3, and SiO2 after doping Sb2O3 were investigated, based on the Jonscher’s universal power law and the Dissado–Hill model. The microstructures were investigated using x-ray diffractometer, scanning electron microscope, energy dispersive spectrometer, and x-ray photoelectron spectrometer. The capacitance–voltage (C–V) method was utilized to obtain the parameters of the double Schottky barrier. The dielectric spectra were analyzed to extract the parameters of defect distribution. The current density–electric field (J–E) characteristics were measured to obtain the parameters of electrical properties. We found that with increasing Sb2O3 content, the ZnO grain size distribution become more homogeneous in the Sb2O3-doped ZnO varistors; the density Zn i × is decreased; except for less homogeneous V O × , more homogeneous distributions of Zn i ∙ in the depletion layers and the extrinsic defects at the interfaces are achieved in the Sb2O3-doped ZnO varistors. Therefore, the enhancement in the electrical properties was achieved by doping Sb2O3 due to the increased number of active grain boundaries per unit volume, i.e. the increased breakdown field and nonlinear coefficient, and the decreased leakage current density. The results of this study suggest that the Jonscher’s universal power law and the Dissado–Hill model can be effectively used to analyze defect distributions in varistor ceramics.

scholarly journals Experimental study on variation law of electrical parameters and temperature rise effect of coal under DC electric field

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Yunpeng Yang ◽  
Zhihui Wen ◽  
Leilei Si ◽  
Xiangyu Xu
Keyword(s):  
Electric Field ◽  
Temperature Rise ◽  
Experimental System ◽  
Gas Production ◽  
Breakdown Field ◽  
Coal Surface ◽  
Electrical Parameters ◽  
Slow Cooling ◽  
Microstructural Changes ◽  
Anthracite Coal

AbstractJoule heats which are generated by coals in an applied electric field are directly correlated with variation resistivity of electrical parameters of coals. Moreover, the joule heating effect is closely related with microstructural changes and relevant products of coal surface. In the present study, a self-developed applied direct current (DC) field was applied onto an experimental system of coals to investigate variation resistivity of electrical parameters of highly, moderately and lowly metamorphic coal samples. Moreover, breakdown voltages and breakdown field intensities of above three coal samples with different metamorphic grades were tested and calculated. Variation resistivity of electrical parameters of these three coal samples in 2 kV and 4 kV DC fields were analyzed. Results show that internal current of all coal samples increases continuously and tends to be stable gradually after reaching the “inflection point” at peak. The relationship between temperature rise effect on anthracite coal surface in an applied DC field and electrical parameters was discussed. The temperature rise process on anthracite coal surface is composed of three stages, namely, slowly warming, rapid warming and slow cooling to stabilize. The temperature rise effect on anthracite coal surface lags behind changes of currents which run through coal samples. There’s uneven temperature distribution on anthracite coal surface, which is attributed to the heterogeneity of coal samples. In the experiment, the highest temperature on anthracite coal surface 65.8 ℃ is far belower than the lowest temperature for pyrolysis-induced gas production of coals 200 ℃. This study lays foundations to study microstructural changes and relevant products on coal surface in an applied DC field.

Effect of K2O on the sintered microstructure of praseodymium-doped ZnO varistors

1989 ◽  
Vol 8 (8) ◽  
pp. 974-976 ◽  
Author(s):  
H. K. Varma ◽  
K. P. Kumar ◽  
K. G. K. Warrier ◽  
A. D. Damodaran
Keyword(s):  
Zno Varistors ◽  
Doped Zno

scholarly journals A Comparative Study between the Effects of Magnetic and Nonmagnetic Dopants on the Properties of ZnO Varistors

2010 ◽  
Vol 2010 ◽  
pp. 1-9 ◽  
Author(s):  
A. Sedky ◽  
E. El-Suheel
Keyword(s):  
Comparative Study ◽  
Nonlinear Coefficient ◽  
Xrd Analysis ◽  
Breakdown Field ◽  
Doping Content ◽  
Leakage Currents ◽  
Electrical Conductivities ◽  
Zno Varistors ◽  
The Difference ◽  
Zno Ceramics

A comparative study between effects of Mn and Al on the properties of ZnO varistor sintered at 1200 is investigated by XRD, SEM hardness, and I-V measurements. Although both Mn and Al do not influence the well-known peaks related to wurtzite structure of ZnO ceramics, some other unknown peaks could be formed at higher doping content (). Also, the shape and size of grains are clearly different for both dopants. Average crystalline diameters, deduced from XRD analysis, are between 42 nm and 62 nm, which are 50 times lower than those obtained from SEM micrographs, while the oxygen vacancies deduced from EDAX analysis, are gradually decreased by doping content for both dopants. Interestingly, the values of breakdown field, nonlinear coefficient and barrier height are found to be higher in Mn samples as compared to Al samples, while the opposite is reported for leakage currents, hardness, and electrical conductivities. The values of are changed from 2.67 V/cm to 41.67 V/cm for Al, and from 1928 V/cm to 6571 V/cm for Mn. The conductivity of Al samples is higher than that of ZnO, and it is nearly (103–105) times the conductivity of Mn samples. These results are discussed in terms of the difference of magnetic moment and valence state between these two additives.

Effects of dc bias on dielectric relaxations in CaCu3Ti4O12 ceramics

2017 ◽  
Vol 29 (6) ◽  
pp. 4488-4494 ◽  
Author(s):  
Kangning Wu ◽  
Yuwei Huang ◽  
Linlin Hou ◽  
Zhuang Tang ◽  
Jianying Li ◽  
...  
Keyword(s):  
Dielectric Relaxations ◽  
Dc Bias

Structural and electronic characteristics of pure and doped ZnO varistors

2012 ◽  
Vol 21 (11) ◽  
pp. 116103 ◽  
Author(s):  
A. Sedky ◽  
E. El-Suheel
Keyword(s):  
Zno Varistors ◽  
Doped Zno

Preparation and Characterization of Manganese Doped ZnO Varistors

2012 ◽  
Vol 476-478 ◽  
pp. 1062-1066
Author(s):  
Jian San Zheng ◽  
Shao Feng Zhu
Keyword(s):  
Zno Varistors ◽  
Doped Zno ◽  
Sintered Temperature

In this paper, the influences of MnO2 and V2O5 on the varistor properties of ZnO- V2O5-based ceramics were examined. The results show that, the addition of MnO2 to the ZnO-V2O5-based ceramics was found to improve varistor properties. The sintered temperature was benefit to enhancing the growth of crystals of the samples and the non-ohomic coefficient can be improved. The samples have non-ohmic coefficient α=27.8 and varistor voltage U1mA=60.9V/mm when they are sintered at 1100°C with 2 hours.

The Effects of Cu Dopant on the Microstructure and Non-Ohmic Electrical Properties of ZnO Varistors

2011 ◽  
Vol 343-344 ◽  
pp. 160-165 ◽  
Author(s):  
Ji Wei Fan ◽  
Xiao Peng Li ◽  
Zhen Guo Zhang ◽  
Zhi Qiang Jiao ◽  
Xiang Yang Liu ◽  
...  
Keyword(s):  
Electrical Property ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Grain Growth ◽  
Electrical Characteristics ◽  
Doping Effects ◽  
Zno Varistors ◽  
Doped Zno ◽  
Cu Dopant ◽  
Good Agreement

The doping effects of Cu on the microstructure and non-ohmic electrical properties of ZnO varistors were studied. Addition of Cu2O can enhance the ZnO grain growth during sintering. The SEM and EDS results revealed that the added Cu mainly distributed in the grain boundary and spinel phases of ZnO varistors. The Cu2O addition increased the both of grain and grain boundary resistances. However it decreased the non-ohmic electrical characteristics of ZnO varistors, which is a good agreement with similar findings on Ag2O additions, but contrasts to the reports of good non-ohmic electrical property which found on binary Cu doped ZnO varistors.

Cyclic Voltammetric Studies of the Behavior of Pb-0.3%Ag-0.06%Ca Rolled Alloy Anode during and after Zinc Electrowinning

2013 ◽  
Vol 750-752 ◽  
pp. 2232-2235 ◽  
Author(s):  
Hai Tao Yang ◽  
Huan Rong Liu ◽  
Yong Chun Zhang ◽  
Bu Ming Chen ◽  
Zhong Cheng Guo ◽  
...  
Keyword(s):  
Electrochemical Behaviour ◽  
Anodic Oxide ◽  
Anodic Peak ◽  
Zinc Electrowinning ◽  
Positive Direction ◽  
Major Phase ◽  
Oxide Layers ◽  
Negative Direction ◽  
Alloy Anode ◽  
Sulphate Electrolyte

In this paper, electrochemical behaviour of Pb0.3%Ag0.06%Ca rolled alloy anode during the 6 days galvanostatic electrolysis in acid zinc sulphate electrolyte solution was investigated with Cyclic Voltammetry (CV) techniques. The phase composition of the anodic oxide layers during the electrolysis was observed using X-Ray Diffraction (XRD). The results revealed that with the increasing electrolysis time, the anodic peak (PbPbSO4) is mainly present a rise trend in the first day electrolysis, thereafter, almostly keep a constant value. And the anodic peak (PbPbSO4) gradually moved in the positive direction while the anodic peak (PbSO4β-PbO2, PbOα-PbO2) strongly moved in the negative direction. The cathodic peak (β-PbO2 and α-PbO2PbSO4) and (PbO and PbSO4Pb) mainly present a rise trend and gradually moved in the negative direction. Besides, the corrosion phase of the anodic oxide layers mainly consist of PbSO4, Pb, α-PbO2 and PbS2O3. After electrolysis for 3 days, the major phase of the anodic oxide layers is PbSO4 with a few Pb phase. When the electrolysis reaches the 6th day, the major phase of the anodic oxide layers is also PbSO4 with a few α-PbO2 phase. The preferred growth orientation of PbSO4 is (021) ,(121) and (212) planes.

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