Relation Between Grain Boundary and Electrical Degradation of ZnO Varistors

2006 ◽  
pp. 117-120
Author(s):  
Masayuki Takada ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Boundary ◽  
Electrical Degradation ◽  
Zno Varistors

Effect of Si and Ba Addition on ZnO Grain Growth and Electrical Characteristics of Bi-Based ZnO Varistors

2013 ◽  
Vol 566 ◽  
pp. 219-222 ◽  
Author(s):  
Atsuko Kubota ◽  
Ai Fukumori ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Electrical Characteristics ◽  
Electrical Degradation ◽  
Zno Varistors

With the goal of fabricating varistors with low varistor voltages, we investigated the effects of adding Ba and Si to BiCoMn-added ZnO varistors on the varistor voltage and the resistance to electrical degradation. Ba2Mn3O8, which reduces the resistance to electrical degradation, was not formed at the grain boundary when Si was added. The resistance to electrical degradation was considerably improved by adding 0.10.15 mol% Si relative to samples to which small amounts of Sb had been added. The varistor voltage increased monotonically with increasing amount of added Si; it was approximately 36 V/mm for 0.1 mol% Si.

Effects of Thermal Annealing for Barium and Silicon-Added Bismuth Based Zinc Oxide Varistors on Electrical Properties and Grain Boundary Structure

2013 ◽  
Vol 582 ◽  
pp. 218-221
Author(s):  
Atsuko Kubota ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Electrical Properties ◽  
Grain Boundary ◽  
Thermal Annealing ◽  
Boundary Structure ◽  
Zno Varistor ◽  
Electrical Degradation ◽  
Grain Boundary Structure ◽  
Zno Varistors ◽  
Short Time ◽  
Zinc Oxide Varistors

In order to fabricate varistors with low varistor voltage, the effects of thermal annealing of CoMnBaSi-added Bi based ZnO varistors on electrical properties and the grain boundary structure were investigated. The varistor voltage for the BiCoMnBaSi-added ZnO varistor decreased in half by thermal annealing for a short time. The resistance to electrical degradation was most improved by the addition of SiO2and thermal annealing for 1020 min. It is suggested that the composition of Bi and Si in the sheet-like deposit is changed by varying the annealing time and the resistance to electrical degradation is improved by both addition of SiO2as well as thermal annealing for short time.

scholarly journals Relation between Grain Boundary and Electrical Degradation of ZnO Varistors

2006 ◽  
Vol 126 (3) ◽  
pp. 105-112 ◽  
Author(s):  
Masayuki Takada ◽  
Hiroyuki Yoshino ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Boundary ◽  
Electrical Degradation ◽  
Zno Varistors

Relation Between Grain Boundary and Electrical Degradation of ZnO Varistors

2006 ◽  
Vol 320 ◽  
pp. 117-120 ◽  
Author(s):  
Masayuki Takada ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Boundary ◽  
Optical Microscopy ◽  
Xrd Analysis ◽  
Twin Plane ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrical Degradation ◽  
Characteristics Analysis ◽  
Zno Varistors ◽  
Doped Zno

The effects of the electrical degradation characteristics and microstructure of Sb2O3-doped ZnO varistors were investigated by optical microscopy, X-ray diffraction (XRD) analysis, and voltage-current (V-I) characteristics analysis. The nonlinearity index α of the V-I characteristics of the Bi-Mn-Co-Sb2O3-doped ZnO varistors decreased with increasing Sb2O3 content after electrical degradation. The twin crystal of ZnO was formed by doping with Sb2O3. The number of twin crystals, of which two c-axes are perpendicular to the twin plane, increased and the number of twin crystals, of which c-axes are parallel to the twin plane, decreased with increasing amount of Sb2O3 doped. It is suggested that electrical degradation is affected by the combination of the orientation of ZnO grains containing twin planes and a double Schottky barrier may not be formed in the twin plane.

Effect of SnO2 Addition on Electrical Degradation of ZnO Varistors

2007 ◽  
Vol 350 ◽  
pp. 213-216 ◽  
Author(s):  
Masayuki Takada ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Boundary ◽  
Integral Intensity ◽  
Local Maximum ◽  
Diffraction Peak ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Ions ◽  
Xrd Diffraction ◽  
Electrical Degradation ◽  
Zno Varistors

The effects of SnO2 addition on the electrical degradation characteristics of Bi2O3-MnO2-Co3O4 -added ZnO varistors were investigated by field-emission scanning electron microscopy (FE-SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), and voltage-current (V-I) characteristics. The ZnO grain size was made uniform by the addition of SnO2 or Sb2O3. The nonlinearity index α of the V-I characteristic for Bi-Mn-Co-SnO2-added samples was approximately 50 and the varistor voltage was 120~140V/mm. The value of α after the electrical degradation showed a local maximum at approximately 0.1mol% added SnO2 and then showed a local minimum at approximately 0.5mol%, similar to the relative integral intensity of the XRD diffraction peak for the (004) plane for a small amount of SnO2 added. It is suggested that the diffusion of oxygen ions through the grain boundary is affected by the change in crystal orientation of ZnO grains at the grain boundary induced by the addition of a small amount of SnO2.

Effect of Mn and Co Addition on Electrical Degradation of ZnO Varistors

2006 ◽  
Vol 301 ◽  
pp. 281-0 ◽  
Author(s):  
Hiroyuki Yoshino ◽  
Masayuki Takada ◽  
Jyunya Morioka ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Boundary ◽  
Structural Changes ◽  
Local Maximum ◽  
Electrical Degradation ◽  
Fluorite Type ◽  
Zno Varistors ◽  
Transient Spectroscopy ◽  
Co Addition ◽  
Capacitance Transient ◽  
Trap Levels

The effects of Mn and Co addition on the electrical degradation of ZnO varistors were investigated on the basis of voltage-current (V-I) characteristics, X-ray diffraction (XRD), capacitance-voltage (C-V) characteristics, and isothermal capacitance transient spectroscopy (ICTS). The optimum Co content for preventing electrical degradation was determined to be approximately 0.5mol% in Bi-Mn(0.5mol%)-Co(0~1.0mol%)-added ZnO varistors. Correlations between the improvement of electrical degradation and the structural changes of additives were investigated by XRD. It is suggested that the crystal structure of a-Bi2O3 at the grain boundary changes to a different structure, such as d-Bi2O3 or Bi7.65Zn0.35O11.38 with a fluorite-type structure, at the optimum Co content. It is speculated that the structural change of Bi2O3 at the grain boundary contributes to the improvement of electrical degradation characteristics. Three trap levels were detected in all Bi-Mn-Co-added samples by ICTS. These trap levels showed a local maximum at the optimum Co content.

Effects of Sb, Zr, or Y addition on Electrical Degradation Characteristics of ZnO Varistors

2011 ◽  
Vol 131 (3) ◽  
pp. 219-224
Author(s):  
Takayuki Watanabe ◽  
Ai Fukumori ◽  
Yuji Akiyama ◽  
Masayuki Takada ◽  
Yuuki Sato ◽  
...  
Keyword(s):  
Electrical Degradation ◽  
Zno Varistors

Effects of Zr and Y Addition on the Electrical Degradation Characteristics of ZnO Varistors

2010 ◽  
Vol 130 (4) ◽  
pp. 394-402 ◽  
Author(s):  
Yuji Akiyama ◽  
Masayuki Takada ◽  
Ai Fukumori ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Electrical Degradation ◽  
Zno Varistors

The Effect of Transition of Valence State of Additives on Electrical Degradation of ZnO Varistors

2002 ◽  
Vol 228-229 ◽  
pp. 233-236
Author(s):  
Yohei Satoi ◽  
Takanori Ishikawa ◽  
Takahiro Kaneyoshi ◽  
Shinzo Yoshikado
Keyword(s):  
Valence State ◽  
Electrical Degradation ◽  
Zno Varistors

scholarly journals Microstructure and Electrical Properties of Low-Voltage Barium Titanate Doped Zinc Oxide Varistor Ceramics

2019 ◽  
Vol 8 (4) ◽  
pp. 2713-2718
Keyword(s):  
Zinc Oxide ◽  
Electrical Properties ◽  
Barium Titanate ◽  
Grain Boundary ◽  
Barrier Height ◽  
Current Density ◽  
Low Voltage ◽  
X Ray ◽  
Highly Nonlinear ◽  
Zno Varistors

In the present, varistor ceramics through the combination of zinc oxide (ZnO) with a perovskite material have become widespread because of their unique properties for a wide range of applications in electronic protection devices. Low-voltage zinc oxide (ZnO) varistors with fast response and highly nonlinear electrical properties for overvoltage protection in an integrated circuit are increasingly significant in the application of low-voltage electronics. The present study highlights the interaction between barium titanate (BaTiO3 ) and ZnO varistors through the employment of solid-state reaction method in the production of low-voltage varistors. The effects of BaTiO3 on the microstructure of ZnO varistors were analyzed through scanning electron microscopy (SEM), energy dispersive X-ray analysis spectroscopy (EDS) and X-ray diffraction (XRD). The EDS analysis and XRD measurements suggest the presence of ZnO and BaTiO3 phases. The electrical properties of BaTiO3 -doped ZnO varistors were examined based on the current density-electric field (J-E) characteristics measurement. The varistor properties showed the nonlinear coefficient (α) from 1.8 to 4.8 with the barrier height (φB) ranged from 0.70 to 0.88 eV. The used of BaTiO3 additive in ZnO varistors produced varistor voltages of 4.7 to 14.1 V/mm with the voltage per grain boundary (Vgb) was measured in the ranges 0.03 to 0.05 V. The lowest leakage current density was 348 µA/cm2 , obtained at the samples containing 12 wt.% BaTiO3 with high barrier height. The reduction in barrier height with increasing BaTiO3 content was associated with the excessive amount of BaTiO3 phase, hence cause the deterioration of active grain boundary due to the variation of oxygen (O) vacancies in the grain boundary.

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