Effect of Ho2O3 Doping on Performance of ZnO Varistor

2008 ◽  
Vol 368-372 ◽  
pp. 507-509
Author(s):  
Zhen Ya Lu ◽  
Yu Xiang Liu ◽  
Zhi Wu Chen ◽  
Jian Qing Wu
Keyword(s):  
Electrical Properties ◽  
Grain Growth ◽  
Nonlinear Coefficient ◽  
High Current ◽  
Zno Varistor ◽  
Current Area ◽  
Electric Filed ◽  
Nonlinear Performance ◽  
Effective Dopant ◽  
Surge Current

The effect of Ho2O3 doping on the electrical properties and microstructure of ZnO base varistor was investigated. It was found that Ho2O3 is an effective dopant for increasing the breakdown electric filed. The Ho2O3 doping can also improve the nonlinear performance both in low and high current area. But excessive doping of Ho2O3 will decrease the withstanding surge current. With 0.8mol% Ho2O3 doping, the varistor samples exhibit a breakdown voltage of about 400V/mm, a nonlinear coefficient of 80 and the withstanding surge current of 8/20μs, waveshape is higher than 5kA. Ho2O3 dopant can hinder ZnO grain growth and make the crystal grains more uniform.

Effect of WO3 Doping on Microstructural and Electrical Properties of ZnO-Pr6O11 Based Varistor Materials

2013 ◽  
Vol 591 ◽  
pp. 54-60
Author(s):  
Xiu Li Fu ◽  
Yan Xu Zang ◽  
Zhi Jian Peng
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Grain Growth ◽  
Doping Level ◽  
Nonlinear Coefficient ◽  
Current Voltage ◽  
Average Grain Size ◽  
Current Voltage Characteristics ◽  
Voltage Performance

The effect of WO3doping on microstructural and electrical properties of ZnO-Pr6O11based varistor materials was investigated. The doped WO3plays a role of inhibitor in ZnO grain growth, resulting in decreased average grain size from 2.68 to 1.68 μm with increasing doping level of WO3from 0 to 0.5 mol%. When the doping level of WO3was lower than 0.05 mol%, the nonlinear current-voltage characteristics of the obtained varistors could be improved significantly with increasing amount of WO3doped. But when the doping level of WO3became higher, their nonlinear current-voltage performance would be dramatically deteriorated when more WO3was doped. The optimum nonlinear coefficient, varistor voltage, and leakage current of the samples were about 13.71, 710 V/mm and 13 μA/cm2, respectively, when the doping level of WO3was in the range from 0.03 to 0.05 mol%.

Research on Mechanism of Improving Electrical Properties of ZnO Varistor Ceramics by Laser Shock Processing

2010 ◽  
Vol 37-38 ◽  
pp. 1045-1049 ◽  
Author(s):  
Rui Fang Chen ◽  
Yin Qun Hua ◽  
Guang Ji ◽  
Zhen Zhen Sun
Keyword(s):  
Phase Composition ◽  
Electrical Properties ◽  
Nonlinear Coefficient ◽  
Voltage Gradient ◽  
Laser Shock ◽  
Electrical Parameters ◽  
Laser Shock Processing ◽  
Zno Varistor ◽  
Compound State ◽  
Shock Processing

In order to improve electrical properties, annealed ZnO varistor ceramics have been treated by laser shock processing (LSP). Electrical parameters of the annealed ZnO varistor ceramics were measured by CJ1001 Varistor Tester. Morphology and microstructure of the annealed ZnO varistor ceramics were gained by XRD and SEM. The results indicate that compared with the electrical properties of the annealed ZnO varistor ceramics, the voltage gradient of the ZnO varistor ceramics treated by LSP remains the same, the nonlinear coefficient substantially increases by 31.6%, and the leakage current reduces by 33.3%. Meanwhile, the phase composition of the annealed ZnO varistor ceramics is mainly composed of ZnO main phase, Zn2.33Sb0.67O4, β-Bi2O3, and δ-Bi2O3 phase; while the phase composition of the ZnO varistor ceramics remains the above four phases in the compound state (anneal and then LSP), but the content of δ-Bi2O3 phase increases. The increase of δ-Bi2O3 phase content is the main reason for improving the electrical properties of the annealed ZnO varistor ceramics.

Effect of Ball Milling of Composite Additives on the Microstructure and Electrical Properties of ZnO Varistors

2011 ◽  
Vol 695 ◽  
pp. 581-584
Author(s):  
Jian Feng Zhu ◽  
Guo Quan Qi ◽  
Hai Bo Yang ◽  
Fen Wang
Keyword(s):  
Electrical Properties ◽  
Ball Milling ◽  
Phase Distribution ◽  
Raw Materials ◽  
Nonlinear Coefficient ◽  
Boundary Phase ◽  
Zno Varistor ◽  
Zno Powders ◽  
Second Phases ◽  
Zno Varistors

ZnO varistors were synthesized with ZnO powders and intensity milled composite additives as raw materials. The effect of milling time of the composite additives on the grain boundary phase distribution as well as the electrical properties was investigated in detail. The results show that ball milling composite additives have a significant effect on the ZnO varistors. The samples derived from ball milled composite additives possess the smaller size and more uniform distribution of the second phases, which improved the electrical properties obviously. The optimal ZnO varistor samples were obtained by ball milling 15 h for the composite additives, which possess average ZnO crystalline grain size of about 4 µm, the gradient voltage V1mA of 454 V/mm, the leakage current IL of 0.12 µA, and the nonlinear coefficient α of 55.

scholarly journals Effect of Ni2O3 Doping on the Electrical Properties and Intrinsic Defect Concentration of ZnO Varistor Ceramics

2020 ◽  
Vol 185 ◽  
pp. 01019
Author(s):  
Qirui Guo ◽  
Lei Zhang ◽  
Fanyi Kong ◽  
Zhaozi Zhang ◽  
Shengtao Li
Keyword(s):  
Electrical Properties ◽  
Electrical Breakdown ◽  
Nonlinear Coefficient ◽  
Defect Concentration ◽  
Electrical Performance ◽  
Breakdown Field ◽  
Intrinsic Defect ◽  
Zno Varistor ◽  
Average Grain Size ◽  
Aging Properties

With the development of high voltage transmission, there is an urgent need to develop ZnO varistor ceramics with high anti-aging properties. The key is to manipulate the intrinsic defect concentration of ZnO varistor ceramics precisely. In this paper, ZnO varistor ceramics doped with different contents of Ni2O3 are taken to study the relationship between the microstructure and electrical properties, and the effect of ZnO varistor ceramics doped with different contents on intrinsic defect concentration is also considered. The results show that, best electrical performance is shown when the content of Ni2O3 is 1.2mol%, the electrical breakdown field E1mA is 356 V/mm, the nonlinear coefficient reaches 32, and the leakage current IL is 3.4 . While the amount of the doped Ni2O3 is more 0.8mol%, a new phase of Co2Cr5Sb5O4 phase is observed from X-ray diffraction. The SEM micrographs showed that the average grain size decreased monotonously from 14.56 m to 5.73 m with the amount of the doped Ni2O3 increased. According to the results of dielectric spectroscopy, the intrinsic defect concentration increased with the contents of the doped Ni2O3 increased. The increase of Zinc interstitial is much greater than that of Oxygen vacancies, which is harmful to Long-term aging characteristics of ZnO varistor ceramics.

Microstructure and Electrical Properties of Doped ZnO Varistor Nanomaterials

2004 ◽  
Vol 99-100 ◽  
pp. 127-132 ◽  
Author(s):  
Xueya Kang ◽  
Tu Minjing ◽  
Ming Zhang ◽  
Wang Tiandiao
Keyword(s):  
Electrical Properties ◽  
Sol Gel ◽  
Nonlinear Coefficient ◽  
Varistor Ceramic ◽  
Homogeneous Microstructure ◽  
Grain Sizes ◽  
Zno Varistor ◽  
Nanometer Materials ◽  
Doped Zno ◽  
Tan Δ

A sol-gel method of preparation doped ZnO varistor nanomaterials is described, The influences of doped ZnO nanomaterials for varistor microstructure and electrical properties (nonlinear coefficient α, breakdown voltage V1mA , dielectric constant ε, and dielectric loss tan δ) are investigated. Compared with the conventional mixed oxide technique, varistor ceramic of prepared by nanometer materials showed a more homogeneous microstructure, smaller grain sizes, higher densities and excellent electrical properties.

Grain boundary structure of A ZnO-Bi2O3-CoO varistor

1990 ◽  
Vol 48 (4) ◽  
pp. 374-375
Author(s):  
Yoko Suyama ◽  
Yoshitsugu Tomokiyo ◽  
Kunihiro Terasaka
Keyword(s):  
High Resolution ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Nonlinear Coefficient ◽  
Analytical Electron Microscopy ◽  
Ceramic Technology ◽  
Boundary Structure ◽  
Oxide Ceramic ◽  
Zno Varistor ◽  
20 Nm

The nonhomic property of ZnO-based varistors has been considered to depend on grain boundary structures. The microstructures of ulticomponent varistors are very complicated and quite sensitive to concentration and thermal history. It is not clear which microstructures play an important role for the electrical properties such as nonlinear coefficient and varistor voltage, and for the degradiation. In the present paper the microstructure of ZnO varistor was investigated by means of analytical electron microscopy to elucidate the relation between the microstructures and the electrical properties. In order to obtain local information on the microstructures of grain boundary and multiple junction, we combined the various TEM techniques such as high-resolution imaging (HREM), microprobe diffraction (μ ED), convergent-beam electron diffraction (CBED) and energy dispersive x-ray spectroscopy (EDX).ZnO varistor samples with addition of 0.5molZ% Bi2O3 + 0∼0.5molZ% CoO were prepared by conventional mixed-oxide ceramic technology. The thin foils prepared from the samples sintered at 800, 900 and 1000 °C were examined either by an analytical TEM, JEM-2000FX at 200 kV or a high resolution TEM, JEM-4000EX at 400 kV. The diameters of electron probe were less than 10 nm for μ ED and about 20 nm for EDX and 10∼20 nm for CBED.

Influence of Pr6O11 on the Characteristics and Microstructure of Zinc Varistors

2008 ◽  
Vol 368-372 ◽  
pp. 500-502 ◽  
Author(s):  
Jian Feng Zhu ◽  
Ji Qiang Gao ◽  
Fen Wang ◽  
Ping Chen
Keyword(s):  
Electrical Properties ◽  
Grain Growth ◽  
Leakage Current ◽  
Threshold Voltage ◽  
Spinel Phase ◽  
Nonlinear Coefficient ◽  
Pyrochlore Phase ◽  
Voltage Ratio ◽  
Zno Crystal ◽  
Microstructural Homogeneity

The influence of the amount of Pr6O11 additions on the microstructure and electrical properties of varistors ceramics in the ZnO-Bi2O3 system was investigated. Samples with a low level of Pr6O11 (0.1wt %) have high microstructural homogeneity, which enhances the nonlinear coefficient greatly, and decreases the leakage current without change of voltage ratio. When the Pr6O11 content reached 7wt%, the ZnO grain growth was restricted and the threshold voltage was improved from 275v/mm to 440v/mm. The additive of Pr6O11 changed the process of creating spinel phase, which came from the decomposition of pyrochlore phase. This type of small size phase has more dragging force on the ZnO crystal, which make the whole materials more uniform and compact.

scholarly journals Microstructural and Nonlinear Properties of Zn-V-Mn-Nb-O Varistor Ceramics with Gd2O3 Substitution for Low Voltage Application

2017 ◽  
Vol 268 ◽  
pp. 181-185 ◽  
Author(s):  
Nor Hasanah Isa ◽  
Zakaria Azmi ◽  
Raba’ah Syahidah Azis ◽  
Zahid Rizwan
Keyword(s):  
Electrical Properties ◽  
Grain Growth ◽  
Leakage Current Density ◽  
Current Density ◽  
Triple Point ◽  
Low Voltage ◽  
Nonlinear Coefficient ◽  
Electrical Field ◽  
Nonlinear Properties ◽  
Voltage Application

The effect of Gd2O3 substitution on the microstructural and electrical properties of Zn-V-Mn-Nb-O varistor ceramics sintered at 900°C was investigated. XRD, SEM, and EDAX results show that the GdMnO3 and GdVO4 phases formed at the grain boundaries and triple point junctions. Gd2O3 substitution inhibited the grain growth from 3.85 to 3.06 μm and increased the sintered ceramics density from 5.12 to 5.19 g/cm3.The samples containing the amount of 0.03 mol% Gd2O3 exhibit an optimum nonlinear coefficient α value which is 9.91, highest breakdown electrical field which is 88.48 V/mm and lowest leakage current density which is 0.11 mA/cm2 in low voltage application.

Study on the Electrical Properties and the Ac Conductance Response of ZnO-Based Varistor

2014 ◽  
Vol 1070-1072 ◽  
pp. 625-629
Author(s):  
Xue Tong Zhao ◽  
Rui Jin Liao ◽  
Jian Ying Li
Keyword(s):  
Activation Energy ◽  
Grain Size ◽  
Electrical Properties ◽  
Electric Field ◽  
Grain Growth ◽  
Relaxation Peak ◽  
Breakdown Electric Field ◽  
Zno Varistor ◽  
Ac Conductance

ZnO-based varistor ceramics with different recipes were prepared in this research. It was found that the grain growth was restrained with the addition of Ba2+. SEM results indicated that the grain size of ZnO varistor ceramics with Ba2+ was reduced to 4.7 μm. Correspondingly, the breakdown electric field of the ZnO varistor samples were extremely enhanced to 8730 V/cm. The results of ac conductance response showed that two relaxation peak 1 and 2 with activation energy at about 0.24 eV and 0.36 eV were observed in 100-250 K, which were not affected by additives. However, a new conductance relaxation peak 3 in 300-450 K for sample B and C can be found, whose activation energy were varied from 0.55 eV to 0.65 eV with the addition of Ba2+. It was put forward that the electrical properties of ZnO varistor ceramics may be associated with the conductance relaxation peak 3.

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