Microstructure and Electrical Properties of La2O3-Doped ZnO-Bi2O3 Based Varistor Ceramics

2009 ◽  
Vol 79-82 ◽  
pp. 2007-2010 ◽  
Author(s):  
Dong Xu ◽  
Xiao Nong Cheng ◽  
Ming Song Wang ◽  
Li Yi Shi
Keyword(s):  
Electrical Properties ◽  
Leakage Current ◽  
Threshold Voltage ◽  
Nonlinear Coefficient ◽  
Voltage Gradient ◽  
Solid Reaction ◽  
Reaction Route ◽  
Doped Zno

La2O3-doped ZnO-Bi2O3-based varistor ceramics were obtained by a solid reaction route, and the microstructure and electrical properties of the varistor ceramics were studied in this paper. The results showed with addition of 0-1.00mol% La2O3, La2O3-doped ZnO-based varistor ceramics were prepared in this paper with the voltage gradient of 77-503V/mm, the nonlinear coefficient of 2.4-36.8, and the leakage current of 0.09-494μA. The results also showed with addition of 0.08mol% La2O3, La2O3-doped ZnO-based varistor ceramics exhibit comparatively ideal comprehensive electrical properties. Such as the threshold voltage was 320V/mm, the nonlinear coefficient was 36.8 and the leakage current was 0.29μA. The doping of La2O3 affects the form and decomposition of the pyrochlore.

Sintering Time Influences on Microstructure and Electrical Properties of Scandium Doped Zinc Oxide Varistor Ceramics

2013 ◽  
Vol 745-746 ◽  
pp. 126-130
Author(s):  
Cheng Hua Zhang ◽  
Bin Jiang ◽  
Ke Zhang ◽  
Lei Jiao ◽  
Ren Hong Yu ◽  
...  
Keyword(s):  
Zinc Oxide ◽  
Electrical Properties ◽  
Nonlinear Coefficient ◽  
Voltage Gradient ◽  
X Ray Diffraction ◽  
Solid Reaction ◽  
Reaction Route ◽  
X Ray ◽  
Sintering Time ◽  
Zinc Oxide Varistor

Sc2O3-doped zinc oxide varistor ceramics were prepared by a solid reaction route. The microstructure and the electrical properties was analyzed by scanning electron microscope and X-ray diffraction. Sintering time influences on the microstructure and the electrical properties of Sc2O3-doped zinc oxide varistor ceramics are studied. The results show that the electrical properties of Sc2O3-doped zinc oxide varistor ceramics sintered at 1000 and sintered for 1 h was better: the voltage gradient was 653 V/mm; the leakage current was 0.18 μA and the nonlinear coefficient was 57.1.

Effect of Technological Parameters on the Microstructure and Electrical Properties of ZnO Varistors

2013 ◽  
Vol 820 ◽  
pp. 208-211
Author(s):  
Li Li ◽  
Qi Bin Liu
Keyword(s):  
Solid State ◽  
Electrical Properties ◽  
Leakage Current ◽  
Sintering Temperature ◽  
Voltage Gradient ◽  
Technological Parameters ◽  
Reaction Route ◽  
Conventional Solid State Reaction ◽  
Zno Varistors ◽  
Solid State Reaction Route

To improve voltage-gradient and to reduce the sintering temperature of ZnO varistors, high voltage-gradient ZnO varistors were synthesized with a conventional solid state reaction route. By means of SEM and DC parameter instrument for varistor, the influence of different technological parameters on microstructure, voltage-gradient and leakage current of ZnO varistors was investigated. The experimental results show that by using the process that presintering the additives at 850°C, the density is improved, the voltage-gradient is increased, and the leakage current is decreased. The optimum voltage-gradient and leakage current are 371V/mm and 3μA, respectively.

Microstructure and Electrical Properties of ZnO–Bi2O3-Based Varistor Ceramics by Different High-Energy Ball Milling Time

2012 ◽  
Vol 490-495 ◽  
pp. 3391-3395
Author(s):  
Cheng Hua Zhang ◽  
Ming Shuang Li ◽  
Dong Xu ◽  
Yong Fang Chen ◽  
Yuan Ling Liu ◽  
...  
Keyword(s):  
Electrical Properties ◽  
Ball Milling ◽  
Leakage Current ◽  
Threshold Voltage ◽  
Nonlinear Coefficient ◽  
High Energy ◽  
Sem Analysis ◽  
High Energy Ball Milling ◽  
Electrical Measurements ◽  
Energy Ball

The microstructure and electrical properties of ZnO-Bi2O3-based varistor ceramics prepared by the high-energy ball milling were studied. The varistor ceramics samples were characterized by XRD and SEM analysis, as well as by dc electrical measurements, such as the nonlinearity coefficients, leakage current and threshold voltage. The best electrical characteristics were found in sample by the high-energy ball milling 1 h and sintered at 1000 °C for 2 h, which exhibited the threshold voltage was 457 V/mm, the nonlinear coefficient was 59.3 and the leakage current was 1.18 μA.

Microstructure and Electrical Properties of Y2O3 and Sb2O3 Co-Doped ZnO-Based Varistors

2014 ◽  
Vol 602-603 ◽  
pp. 830-835
Author(s):  
Xiu Li Fu ◽  
Yan Xu Zang ◽  
Zhi Jian Peng
Keyword(s):  
Electrical Properties ◽  
Leakage Current ◽  
Breakdown Voltage ◽  
Nonlinear Coefficient ◽  
Current Increase ◽  
Atom Ratio ◽  
Mean Size ◽  
Doped Zno ◽  
Co Doped ◽  
Better Than

Through a conventional ceramic process, Y2O3 and Sb2O3 co-doped ZnO-based varistors were prepared. The microstructure and electrical properties of the as-prepared varistors were investigated. Y2O3 could act as an inhibitor to the growth of ZnO grains when working with Sb2O3. The mean size of ZnO grains in the Sb2O3 and Y2O3 co-doped samples was smaller than those of the samples only added with Y2O3 or Sb2O3. And with appropriately increased ratio of Y:Sb, it would result in increased sample densification. When the doping level of Y2O3 was small, the nonlinear coefficientand breakdown voltage of the varistors would increase with increasing doping amounts of Y2O3, and the leakage current would decrease. However, when Y2O3 was doped without Sb2O3, both the nonlinear coefficientand breakdown voltage of the varistors would decrease sharply, thus the leakage current increase dramatically. The electrical properties of the Sb2O3 and Y2O3 co-doped varistors would be better than those of the samples only added with Y2O3 or Sb2O3, and when the Y:Sb atom ratio was 5, the nonlinear coefficients, breakdown voltages and leakage current of the varistors reached their optimum values of 777 V/mm, 23 and 0.17 mA/cm2, respectively.

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.

Electrical Properties of a TiO2-SrO Varistor System

2014 ◽  
Vol 975 ◽  
pp. 168-172
Author(s):  
Tiago Delbrücke ◽  
Igor Schmidt ◽  
Sergio Cava ◽  
Vânia Caldas Sousa
Keyword(s):  
Titanium Dioxide ◽  
Electrical Properties ◽  
Field Strength ◽  
Leakage Current ◽  
Low Voltage ◽  
Nonlinear Coefficient ◽  
Breakdown Field ◽  
Strontium Oxide ◽  
Breakdown Field Strength

The addition of different dopants affects the densification and electrical properties of TiO2 based varistor ceramics. The nonlinear current (I) and voltage (V) characteristics of titanium dioxide are examined when doped with small quantities (0.5-2 at.%) of strontium oxide. This paper discusses the electrical properties of such an SrO doped TiO2 system, and demonstrates that some combinations produce electrical properties suitable for use as low voltage varistors. The high value of the nonlinear coefficient (α) (6.6), the breakdown field strength (Eb) (328 V/cm) and the leakage current (Ir) (0.22 mA/cm2) obtained in a system newly doped with SrO, are all adequate properties for application in low voltage varistors.

Influence of CeO2-Doping on the Electrical Properties of ZnO-Bi2O3-Based Varistor Ceramics

2016 ◽  
Vol 697 ◽  
pp. 262-266
Author(s):  
Zhan Chuan Cao ◽  
Liao Ying Zheng ◽  
Li Hong Cheng ◽  
Tian Tian ◽  
Guo Rong Li
Keyword(s):  
Grain Size ◽  
Phase Composition ◽  
Detection Limit ◽  
Electrical Properties ◽  
Barrier Height ◽  
Nonlinear Coefficient ◽  
Donor Concentration ◽  
Average Grain Size ◽  
Doped Zno ◽  
Density Of Interface States

The microstructure and electrical properties of CeO2-doped ZnO-Bi2O3-based varistors were investigated for different amounts of the dopant. The phase composition of CeO2-doped samples was similar to the undoped samples. Ce mainly segregated at the grain boundaries within the EDS detection limit. The average grain size decreased from 7.3 to 6.7 μm and the breakdown voltage increased from 438 to 501 V/mm when the content of CeO2 ranged from 0 to 0.2 mol%. The nonlinear coefficient increased from 38 to 51 when the content of CeO2 increased from 0 to 0.1 mol%., but the further doping caused it to decrease up to 44 at 0.2mol%. The leakage current decreased from 1 to 0.4 μA/cm2 when the content of CeO2 ranged from 0 to 0.1 mol%. Then it increased to 0.7 μA/cm2 at 0.2 mol%. The density of interface states, the barrier height and the donor concentration increased when the content of CeO2 ranged from 0 to 0.1 mol%, but decreased at 0.2 mol%. Hence, when the content ranges from 0 to 0.1 mol%, CeO2 acts as a donor and can improve the electrical properties.

Grain Boundary Characteristics of 0.01 mol%V2O5-Doped ZnO-Bi2O3-Based Varistor Ceramics

2011 ◽  
Vol 320 ◽  
pp. 240-243
Author(s):  
Jin Hua Ju ◽  
Hua Wang ◽  
Ji Wen Xu
Keyword(s):  
Grain Boundary ◽  
Nonlinear Coefficient ◽  
Voltage Gradient ◽  
Layer Width ◽  
Donor Density ◽  
Average Grain Size ◽  
Grain Boundary Characteristics ◽  
Doped Zno ◽  
Boundary Characteristics ◽  
Density Of Interface States

The effect of 0.01 mol%V2O5 on the grain boundary characteristics of ZnO-Bi2O3-based varistor ceramics is investigated in this work. The average grain size of ZnO was 13.3 µm. The ZnO-Bi2O3 system added with V2O5 content of 0.01 mol% exhibited not only a high nonlinearity, in which the nonlinear coefficient is 25 and the leakage current density is 0.02 µA/mm2 and the voltage gradient of 31.1 V/mm, but also a good grain boundary characteristics, in which barrier height fB = 0.908 eV, depletion layer width w = 32.49 nm, donor density Nd = 0.810×1018 cm-3, and density of interface states Ns = 2.632×1012 cm-2.

Study on Microstructure of ZnO Lighting Arrester with High Voltage Gradient

2011 ◽  
Vol 415-417 ◽  
pp. 1070-1073
Author(s):  
Mo He ◽  
Qi Bin Liu ◽  
Chang Qi Xia
Keyword(s):  
Electrical Properties ◽  
Leakage Current ◽  
High Voltage ◽  
Sintering Temperature ◽  
Holding Time ◽  
Experimental Results ◽  
Voltage Gradient ◽  
Volume Method ◽  
Mass Volume

To obtain ZnO arrester with high voltage gradient and small size, through the optimizing foundamental formula of arrester and changing sintering temperature and holding time, the electrical properties and microstructure of varistors were studied. The density of varistors was determined by using the mass - volume method , voltage gradient and leakage current of ZnO arrester were measured with Ⅱ Surge Arrester Tester DC parameters, microstructure of varistor ceramics were studied by means XRD and SEM. The experimental results show that with increasement of the sintering temperature, the density of varistors increases, and the voltage gradient continues to decrease and leakage current almost keeps unchangable. As the holding time increases, while as the voltage gradient continues to decrease, and leakage current almost unchanges.

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