scholarly journals Simultaneously Enhanced Potential Gradient and Nonlinearity of ZnO Varistor Ceramics by MnO Doping with Nano-Sized ZnO Powders

Materials ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 7748
Author(s):  
Yao Wang ◽  
Zongke Hou ◽  
Jianying Li ◽  
Kangning Wu ◽  
Jiguang Song ◽  
...  
Keyword(s):  
Grain Size ◽  
Schottky Barrier Height ◽  
Nonlinear Coefficient ◽  
Potential Gradient ◽  
Potential Method ◽  
Moderate Amount ◽  
Zno Varistor ◽  
Average Grain Size ◽  
Zno Powders ◽  
Density Of Interface States

ZnO varistor ceramics with a high potential gradient, as well as a high nonlinear coefficient, were reported and analyzed in this paper. With the use of nano-sized ZnO powders, the average grain size was reduced to about 2.6 μm, which successfully raised the potential gradient to 1172 V/mm. Moreover, the nonlinear coefficient increased to 48, and the leakage current was decreased to 8.4 μA/cm2 by doping a moderate amount of MnO (0.9 mol%). This was proven to be caused by the high Schottky barrier height formed at the grain boundary, where the Mn element segregated and, consequently, led to the increased density of interface states. Therefore, this could be considered as a potential method to simultaneously enhance the potential gradient and the nonlinear coefficient of ZnO varistor ceramics.

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.

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%.

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.

scholarly journals Effect of Co3O4 Doping on Nonlinear Coefficient in Zn-Bi-Ti-O Varistor Ceramics

2015 ◽  
Vol 1107 ◽  
pp. 20-26 ◽  
Author(s):  
Mohd Sabri Mohd Ghazali ◽  
Azmi Zakaria ◽  
Wan Rafizah Wan Abdullah ◽  
Mohd Zaid Mohd Hafiz ◽  
Khamirul Amin Matori
Keyword(s):  
Grain Size ◽  
Data Analysis ◽  
Nonlinear Coefficient ◽  
Oxide Ceramics ◽  
Geometrical Method ◽  
Sintering Time ◽  
Current Voltage ◽  
Average Grain Size ◽  
Current Voltage Characteristics ◽  
Sintering Conditions

In the ZnO based varistor, the improvement of nonlinear coefficient (α) and prevention of evaporation of Bi2O3 during heat treatments can be achieved by the addition of MnO2 or Co3O4. In this conjunction, it is proper to see the effect of these additives at different low mol percentage and sintering conditions to nonlinear coefficient improvement of the varistor ceramics. In this paper, the investigation regarding to the α variation of Co3O4 doping on ZnO-Bi2O3-TiO2 system is discussed. Here, the crystalline phases were identified by an XRD (PANalytical (Philips) XPert Pro PW3040/60) with CuKα radiation and the data were analyzed by using XPert High Score software. The density of varistor ceramics was measured by the geometrical method. The current-voltage characteristics of the varistor ceramics were evaluated. The average grain size (d) was determined by lineal intercept method. The α of ZnO doped with 0.5 mol% of Bi2O3, 0.5 mol% of TiO2 and x mol% of Co3O4 was calculated from data analysis of current-voltage characteristics obtained through a Source Measure Unit (Keithley 236). The calculation of α is done by using Origin Pro8.0 software. The value of α at low concentration at 1170 °C has the value 5.36 and 3 at 45 and 90 min sintering time, respectively, and then decreases to 4.99 and 2.98 at 0.8 mol% Co3O4 concentrations. When the amount of dopant is increased then the value of α increase up to 0.4 mol% and then the value are slightly dropped after further addition. The addition of Co3O4 dopant in Zn-Bi-Ti oxide ceramics sintered at 45 minutes cause the value of α to increase up to 0.4 mol% and decrease after further addition.

Effect of Composite Additives on ZnO Varistor Ceramics

2011 ◽  
Vol 687 ◽  
pp. 21-25 ◽  
Author(s):  
Jian Feng Zhu ◽  
Guo Quan Qi ◽  
Hai Bo Yang ◽  
Fen Wang
Keyword(s):  
Electrical Properties ◽  
Ball Milling ◽  
Decomposition Method ◽  
High Energy ◽  
Microscopic Structure ◽  
Linear Coefficient ◽  
Zno Varistor ◽  
Average Grain Size ◽  
Zno Powders ◽  
Energy Ball

ZnO-based varistor ceramics were prepared by sintering ZnO powders with minor additives that were synthesized by standard ball milling, high energy ball milling for 10 h, and pyrogenic decomposition of nitrate. The microscopic structure and composition were analyzed by SEM and XRD respectively, and the electrical properties were investigated by a DC parameter instrument for varistors. Influences of composite additives on composition, microstructure, and electrical properties of ZnO-based varistors were studied. The ZnO varistor with optimum performance is prepared by the pyrogenic decomposition method and it has an average grain size of 5 µm and possesses a varistor voltage of about 561 V/mm, non linear coefficient of 75, and leakage current of 0.45 µA.

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.

scholarly journals EFFECT OF MNO2 DOPING ON NONLINEAR COEFFICEINT OF ZN-BI-TI-O VARISTOR CERAMICS

2016 ◽  
Vol 78 (3) ◽  
Author(s):  
Mohd Sabri Mohd Ghazali ◽  
Wan Rafizah Wan Abdullah ◽  
Azmi Zakaria ◽  
Zahid Rizwan ◽  
Khamirul Amin Matori ◽  
...  
Keyword(s):  
Grain Size ◽  
Data Analysis ◽  
Nonlinear Coefficient ◽  
Oxide Ceramics ◽  
Geometrical Method ◽  
Crystalline Phases ◽  
Sintering Time ◽  
Current Voltage ◽  
Average Grain Size ◽  
Current Voltage Characteristics

The work aims the improvement of nonlinear coefficient ( ) can achieve by the addition of MnO2. The investigation regarding to the variation of MnO2 doping on ZnO-Bi2O3-TiO2 system is discussed. The crystalline phases were identified by an XRD (PANalytical (Philips) X’Pert Pro PW3040/60) with CuK  radiation and the data were analyzed by using X’Pert High Score software. The density of varistor ceramics was measured by the geometrical method. The current-voltage characteristics of the varistor ceramics were evaluated. The average grain size ( ) was determined by lineal intercept method. The  of ZnO doped with 0.5 mol% of Bi2O3, 0.5 mol% of TiO2 and x mol% of MnO2 was calculated from data analysis of current-voltage characteristics obtained through a Source Measure Unit (Keithley 236). The calculation of is done by using Origin Pro8.0 software which at low concentration at 1170 oC has the value 10.36 and 9.21 at 45 and 90 min sintering time, respectively, and then decreases to 5.63 and 5.27 at 0.8 mol% MnO2 concentrations. The addition of MnO2 dopant in Zn-Bi-Ti oxide ceramics sintered at 45 minutes cause the value of  to increase up to 0.4 mol% and decrease after further addition.

Synthesis of Pr6O11 Doped ZnO-Based Varistors by Pyrogenic Decomposition of Nitrate

2011 ◽  
Vol 675-677 ◽  
pp. 179-182
Author(s):  
Jian Feng Zhu ◽  
Guo Quan Qi ◽  
Hai Bo Mao ◽  
Hai Bo Yang ◽  
Fen Wang
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Leakage Current ◽  
Sintering Temperature ◽  
Linear Coefficient ◽  
Average Grain Size ◽  
Non Linear ◽  
Different Temperatures ◽  
Zno Powders ◽  
Doped Zno

Pr6O11 doped ZnO-based varistor powders were prepared by a method of pyrogenic decomposition nitrate, which were together with ZnO powders, made into rounded mass and sintered at different temperatures. The effects of sintering temperatures on the composition, microstructure and electrical properties of Pr6O11 doped ZnO-based varistors were investigated. The results show that the optimum sintering temperature is at 1150 °C with 6 μm ZnO average grain size and the samples possess the advantageous electrical properties: varistor voltage of about 480 V/mm, non linear coefficient reaching 44 and leakage current of 0.7 μA.

Synthesis and Characterization of Hexagonal Shaped Nanocrystalline Zinc Oxide Powders

2012 ◽  
Vol 2 (2) ◽  
pp. 61-76 ◽  
Author(s):  
M. Ahmad ◽  
E. Ahmed ◽  
N. R. Khalid ◽  
M. J. Jackson ◽  
W. Ahmed
Keyword(s):  
Grain Size ◽  
Elevated Temperatures ◽  
Combustion Process ◽  
Combustion Method ◽  
X Ray Diffraction ◽  
Wurtzite Phase ◽  
X Ray ◽  
Heat Treated ◽  
Average Grain Size ◽  
Zno Powders

Nanocrystalline ZnO powders are synthesized using a quick, simple and inexpensive combustion method. Glycine and zinc nitrate, used as fuel and oxidant/cation sources respectively, were mixed together at room temperature to form a slurry or gel. A series of experiments were performed to synthesize nanoparticles for different fuel to oxidant ratios. The rate of heating and stirring greatly influenced the combustion process. The as-synthesized powder was heat treated at elevated temperatures for varying time to remove adsorbed impurities from the surface of the ZnO nanoparticles. Both the as-synthesized and heat treated powders were characterized using a variety of analytical techniques. The hexagonal wurtzite phase of the ZnO powder was revealed from x-ray diffraction measurements. A decrease in the x-ray diffraction density (Dx) and the bulk density (D) resulted in an increase in percentage porosity (%P) of as-synthesized and heat treated ZnO powders. The range of fuel to oxidant ratios used in the present work indicates that they had a strong influence on the grain size of ZnO powders. The average grain size estimated by using the Scherer formula indicated an approximate value of 6-21 nm for the as-synthesized and heat treated samples.

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