Fabrication of High Performance Multilayer ZnO Varistors with Chemically Synthesized Doped Zinc Oxide Powder

2007 ◽  
Vol 336-338 ◽  
pp. 739-742 ◽  
Author(s):  
Lan Yi Wang ◽  
Cheng Xiang Lu ◽  
Guo Yi Tang
Keyword(s):  
Electrical Properties ◽  
Mixed Oxide ◽  
High Performance ◽  
Nonlinear Coefficient ◽  
Oxide Powder ◽  
Homogeneous Distribution ◽  
Dopant Distribution ◽  
Fine Grain ◽  
Zno Varistors ◽  
Zno Powder

Two types of multilayer ZnO varistors are prepared by the chemically synthesized (CS) powder and the mixed oxide (MO) powder. The ceramic microstructure analysis shows that the multilayer variestor (MLV) ceramic prepared by the CS powder has the fine grain, the homogeneous distribution of grain size and the uniform dopant distribution. The CS powder prepared multilayer ZnO varistors display better electrical properties, including higher nonlinear coefficient, higher breakdown voltage, higher peak current, lower leakage current and lower clamping voltage, than those made by the mixed oxide powder. All these superior electrical properties are attributed to the CS powder, which makes more uniform dopant distribution throughout the multilayer ZnO varistors. The homogeneous distribution for the various dopants in the varistor ceramic has been achieved by the chemically synthesized doped ZnO powder. Therefore, the chemically synthesized powder can be used in the manufacture of high performance multilayer ZnO varistors.

Microchemistry of ZnO Varistors

1992 ◽  
Vol 50 (2) ◽  
pp. 1694-1695
Author(s):  
K. K. Soni ◽  
J. Hwang ◽  
V. P. Dravid ◽  
T. O. Mason ◽  
R. Levi-Setti
Keyword(s):  
Grain Boundaries ◽  
Multiple Roles ◽  
Grain Boundary Engineering ◽  
Ion Microprobe ◽  
Dopant Distribution ◽  
Important Ingredient ◽  
Zno Varistor ◽  
Zno Varistors ◽  
Zno Powder ◽  
The University

ZnO varistors are made by mixing semiconducting ZnO powder with powders of other metal oxides e.g. Bi2O3, Sb2O3, CoO, MnO2, NiO, Cr2O3, SiO2 etc., followed by conventional pressing and sintering. The non-linear I-V characteristics of ZnO varistors result from the unique properties that the grain boundaries acquire as a result of dopant distribution. Each dopant plays important and sometimes multiple roles in improving the properties. However, the chemical nature of interfaces in this material is formidable mainly because often trace amounts of dopants are involved. A knowledge of the interface microchemistry is an essential component in the ‘grain boundary engineering’ of materials. The most important ingredient in this varistor is Bi2O3 which envelopes the ZnO grains and imparts high resistance to the grain boundaries. The solubility of Bi in ZnO is very small but has not been experimentally determined as a function of temperature.In this study, the dopant distribution in a commercial ZnO varistor was characterized by a scanning ion microprobe (SIM) developed at The University of Chicago (UC) which offers adequate sensitivity and spatial resolution.

Nonlinear Electrical Properties of (Sc, Ta) Doped TiO2 Varistor Ceramics

2007 ◽  
Vol 280-283 ◽  
pp. 289-292 ◽  
Author(s):  
Wen Bin Su ◽  
Jin Feng Wang ◽  
Hong Cun Chen ◽  
Guo Zhong Zang ◽  
Peng Qi ◽  
...  
Keyword(s):  
Dielectric Constant ◽  
Electrical Properties ◽  
Crystal Lattice ◽  
Nonlinear Coefficient ◽  
Relative Dielectric Constant ◽  
Donor Concentration ◽  
Varistor Ceramic ◽  
Electrical Field ◽  
Schottky Type ◽  
Zno Varistors

The nonlinear electrical properties of TiO2-based varistor doped with 0.25mol% Ta2O5 and different contents of Sc2O3 were investigated. It was found that the TiO2 varistor ceramic doped with 0.10mol% Sc2O3 exhibited an optimal nonlinear coefficient of 7.8, a breakdown electrical field of 16.0V/mm, and relative dielectric constant of 1.27 × 105 (measured at 1 kHz). In order to analyze the effect of Sc2O3 on TiO2 varistors, studies were made on the capacitance versus voltage characteristics. A Schottky-type barrier, which is assumed as the origin of varistor behavior, was inferred from the C-V measurement. The barrier height and donor concentration were obtained as 0.41eV and 1.21 × 1026cm-3, respectively, for sample doped with 0.10mol% Sc2O3. Analogized to the ZnO varistors, the formation mechanism of Schottky-type barrier was discussed in this paper by the theory of defect in crystal lattice.

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.

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.

Effect of B2O3 Doping on the Microstructure and Electrical Properties of ZnO-Based Varistors

2008 ◽  
Vol 368-372 ◽  
pp. 497-499 ◽  
Author(s):  
Feng Hua Liu ◽  
Gao Jie Xu ◽  
Lei Duan ◽  
Ya Li Li ◽  
Ping Cui
Keyword(s):  
Grain Size ◽  
Electrical Properties ◽  
Nonlinear Coefficient ◽  
Solid State Reaction Method ◽  
Electrical Measurements ◽  
Conventional Solid State Reaction ◽  
Reaction Method ◽  
B2o3 Content ◽  
Zno Varistors ◽  
Doped Zno

B2O3 doped ZnO-Bi2O3-Sb2O3-based varistors were fabricated by conventional solid state reaction method. The structure and electrical properties were investigated by XRD, SEM and electrical measurements. The grain size obviously increases with increasing B2O3 content, while the content of Zn7Sb2O12 spinel on the grain boundaries gradually decreases, which implies that B2O3 doping inhibits the growth of Zn7Sb2O12 spinel. The density (ρ) of ZnO varistors increases with increasing B2O3 content (x) and reaches the maximum at x = 0.4 mol%. The sample with x ≈ 0.6 mol% sintered at 1150 °C exhibits the best performance, with nonlinear coefficient of 48 and leakage current of 4 μA.

Dielectric and electrical properties of La@NiO SNPs for high-performance optoelectronic applications

2021 ◽  
Author(s):  
Mohd. Shkir ◽  
Aslam Khan ◽  
Kamlesh V. Chandekar ◽  
M.A. Sayed ◽  
Ahmed Mohamed El-Toni ◽  
...  
Keyword(s):  
Electrical Properties ◽  
High Performance ◽  
Optoelectronic Applications

Ionic Conductivities of Doped CeO2 Thin Films as Related to Their Microstructure

1995 ◽  
Vol 411 ◽  
Author(s):  
Chunyan Tian ◽  
Siu-Wai Chan
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Ionic Conductivities ◽  
Dielectric Constants ◽  
Grain Structure ◽  
X Ray Diffraction ◽  
Fine Grain ◽  
Brick Layer Model ◽  
Columnar Grain ◽  
Beam Deposition

ABSTRACTThin films of 4% Y2O3 doped CeO2/Pd film/(001)LaA103 with a very low pinhole density were successfully prepared using electron-beam deposition technique. The microstructure of the films was characterized by x-ray diffraction and the electrical properties were studied as a function of temperature with AC impedance spectroscopy. A brick layer model was adopted to correlate the electrical properties to the microstructure of the films, which can be simplified as either a series or a parallel equivalent circuit associated with either a fine grain or a columnar grain structure, respectively. The conductivities of the films fell between the conductivities derived from the two circuit models, suggesting that the films are of a mixed fine grain and columnar grain structure. The measured dielectric constants of the films were found smaller than that of the bulk.

scholarly journals Structural and Electrical Studies on ZnO-Based Thin Films by Laser Irradiation

2016 ◽  
Vol 2016 ◽  
pp. 1-6 ◽  
Author(s):  
Shanyue Zhao ◽  
Yinqun Hua ◽  
Ruifang Chen ◽  
Jian Zhang ◽  
Ping Ji
Keyword(s):  
Thin Films ◽  
Grain Size ◽  
Electrical Properties ◽  
Grain Boundaries ◽  
Laser Irradiation ◽  
Nonlinear Coefficient ◽  
Acceptor State ◽  
Xrd Pattern ◽  
Electrical Studies ◽  
Structural And Electrical Properties

The effects of laser irradiation on the structural and electrical properties of ZnO-based thin films were investigated. The XRD pattern shows that the thin films were highly textured along thec-axis and perpendicular to the surface of the substrate. Raman spectra reveal that Bi2O3segregates mainly at ZnO-ZnO grain boundaries. After laser irradiation processing, the grain size of the film was reduced significantly, and the intrinsic atomic defects of grain boundaries and Bi element segregated at the grain boundary were interacted frequently and formed the composite defects of acceptor state. The nonlinear coefficient increased to 24.31 and the breakdown voltage reduced to 5.34 V.

SrTiO3 Based Dual-Functional Ceramics with Nano-Additives

2007 ◽  
Vol 336-338 ◽  
pp. 793-795 ◽  
Author(s):  
Hui Ming Ji ◽  
Xiao Chuan Liu ◽  
Ying Lv ◽  
Cui Xia Li ◽  
Xiao Dong Chen
Keyword(s):  
Electrical Properties ◽  
Nonlinear Coefficient ◽  
Liquid Phase Sintering ◽  
Composite Powders ◽  
Voltage Sensing ◽  
Reducing Atmosphere ◽  
Dual Functional ◽  
Donor And Acceptor ◽  
Nano Additives ◽  
Functional Ceramics

The electrical properties and microstructures of SrTiO3 based voltage-sensing and dielectric dual-functional ceramics with nanometer donor and acceptor additives were studied. The La2O3 nanopowders and MnO-SiO2-Al2O3 (or CuO-SiO2-Al2O3) nano-composite powders were incorporated into SrTiO3 as donor, acceptor and liquid-phase sintering aids. Then semiconducting SrTiO3-based ceramics were sintered at 1360-1440oC for 2 h in a reducing atmosphere. The effects of the nanometer donor and acceptor additives and the sintering temperature on the electrical properties and microstructures of materials were discussed. The results showed that SrTiO3-based varistor ceramics with 1.1 mol% La2O3 and 0.1 mol% MnO nano-additives sintered at 1360-1420oC in graphite and N2 reducing atmosphere have excellent voltage-sensing and dielectric characteristics. The varistor voltage ranges from 2.3 to 5.3 V/mm, the nonlinear coefficient from 3.0 to 3.8, and the dielectric constant from 215,600 to 413,000.

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