Effect of Ba Addition on Electrical Characteristics of Bi-Based ZnO Varistors

2010 ◽  
Vol 445 ◽  
pp. 241-244 ◽  
Author(s):  
Ai Fukumori ◽  
Masayuki Takada ◽  
Yuji Akiyama ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Breakdown Voltage ◽  
Electrical Characteristics ◽  
Zno Varistor ◽  
Electrical Degradation ◽  
Poor Tolerance ◽  
Zno Varistors ◽  
Molten Phase

With the goal of fabricating low-breakdown-voltage varistors, the effect of adding Ba to ZnO varistors on the ZnO grain size was investigated. Grain growth of ZnO could be markedly promoted by adding both Ba and Bi. The maximum grain size was approximately 150 μm and the minimum varistor voltage was approximately 12 V/mm. However, it had relatively poor tolerance characteristics for electrical degradation. It is speculated that when adding both Ba and Bi to a Mn–Co-added ZnO varistor, it is necessary to form the molten phases of Ba and Bi to promote grain growth of ZnO. It is also conjectured that the growth of ZnO grains is not promoted when Ba and Bi do not coexist in the molten phase because Ba forms compounds with Mn independently with the addition of small amounts of Bi.

Effect of Sb Addition on ZnO Grain Growth and Electrical Characteristics of Bi–Co–Mn–Ba-Added ZnO Varistors

2011 ◽  
Vol 485 ◽  
pp. 253-256 ◽  
Author(s):  
Ai Fukumori ◽  
Takayuki Watanabe ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Electrical Characteristics ◽  
Electrical Degradation ◽  
Zno Varistors

With the goal of fabricating varistors with low breakdown voltages (varistor voltages), the effect of adding Sb to Bi-Co-Mn-Ba-added ZnO varistors on the ZnO grain size was investigated. To obtain a uniform ZnO grain size without reducing the grain size, a small amount (e.g., 0.01 mol%) of Sb was added as an additive. This addition suppresses the variation in the ZnO grain size without reducing the grain size. It also improved the resistance to electrical degradation because compounds of Ba and Mn were not formed.

Effect of Simultaneous Addition of Zr and Y on Electrical Characteristics of ZnO Varistors

2011 ◽  
Vol 485 ◽  
pp. 257-260 ◽  
Author(s):  
Takayuki Watanabe ◽  
Ai Fukumori ◽  
Yuji Akiyamna ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Leakage Current ◽  
Nonlinear Coefficient ◽  
The Other ◽  
Electrical Characteristics ◽  
Simultaneous Addition ◽  
Zno Varistor ◽  
Low Leakage ◽  
Electrical Degradation ◽  
Low Leakage Current ◽  
Zno Varistors

The effect of simultaneously adding Zr and Y to Bi–Mn–Co–Sb–Si–Cr–Ni-added ZnO varistors (having the same composition as a commercial varistor) on the varistor voltage, leakage current, and resistance to electrical degradation were investigated. Varistor voltage increased with increasing amount of Y for addition of 0–2 mol % Zr. On the other hand, the nonlinear coefficient α prior to electrical degradation changed very little on the addition of both Y and Zr. With the addition of approximately 1 mol% Zr, the leakage current decreased with increasing amount of Y added. A ZnO varistor with a varistor voltage of approximately 600 V/m, a low leakage current, and excellent resistance to electrical degradation was fabricated by adding approximately 2 mol% Y and approximately 1 mol% Zr.

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

2010 ◽  
Vol 445 ◽  
pp. 237-240 ◽  
Author(s):  
Yuji Akiyama ◽  
Ai Fukumori ◽  
Masayuki Takada ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Electrical Degradation ◽  
Zno Varistors

The effects of the addition of Y or both Y and Zr to Bi-Mn-Co-Sb-Si-Cr-Ni-added ZnO varistors on the varistor voltage and the tolerance characteristics of electrical degradation were investigated. The deterioration of the tolerance characteristics of electrical degradation by the addition of Y was probably caused by an increase in the number of willemite (Zn2SiO4)-type particles or a decrease in the number of spinel (Zn2.33Sb0.67O4)-type particles, but this deterioration was reduced by adding Zr. Moreover, the reduction in the average ZnO grain size due to the addition of Y was a major factor in the increased varistor voltage, and the ZnO grain growth was inhibited by the formation of an un-known compound after adding Y. The varistor voltage of a varistor with 2 mol% added Y increased by approximately 50% compared to a varistor with no Y added.

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.

Gas Sensing Behavior of Porous ZnO Varistors Densified via Rate Controlled Sintering

1996 ◽  
Vol 431 ◽  
Author(s):  
Gaurav Agarwal ◽  
Robert F. Speyer
Keyword(s):  
Grain Size ◽  
Gas Sensor ◽  
Breakdown Voltage ◽  
Gas Sensing ◽  
Hydrogen Gas ◽  
Adsorbed Oxygen ◽  
Intergranular Porosity ◽  
Zno Varistor ◽  
Rate Controlled ◽  
Zno Varistors

AbstractA hydrogen gas sensor based on shift in breakdown voltage of a ZnO varistor was developed. Changes in rate controlled sintering schedules resulted in significant variations in microstructure. Microstructures showing more intergranular porosity and finer grain size demonstrated a comparatively more linear and broad response to H2 concentration. A mechanism for the shift in breakdown voltage based on adsorbed oxygen is suggested for this unique and potentially very useful sensor.

Effect of Sb Addition on the Electrical Characteristics of Bi-Based ZnO Varistors Containing Zr and Y

2013 ◽  
Vol 566 ◽  
pp. 223-226
Author(s):  
Takayuki Watanabe ◽  
Yosuke Tokoro ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Boundaries ◽  
Leakage Current ◽  
High Resistance ◽  
Electrical Characteristics ◽  
Zno Varistor ◽  
Low Leakage ◽  
Electrical Degradation ◽  
Low Leakage Current ◽  
Zno Varistors

The effects of adding Sb to a BiMnCoSiCrNiYZr-added ZnO varistor (with the same composition as a commercial varistor) on the varistor voltage, leakage current, and resistance to electrical degradation were investigated. Bi is incorporated in spinel particles, and δ-Bi2O3eventually disappears with the addition of small amounts of Bi, especially as the amount of Sb2O3added increased. Reduction in both the nonlinearity index and the amount of δ-Bi2O3for small amounts of added Bi with the addition of more than approximately 1.25 mol% Sb2O3demonstrates that Sb inhibits Bi2O3from forming deep interfacial impurity levels at the grain boundaries. The sample containing 1.2 mol% Bi2O3, 1.0 mol% ZrO2, 1.0 mol% Y2O3, and 1.5 mol% Sb2O3added exhibits a high varistor voltage (approximately 630 V/mm), high resistance to electrical degradation and low leakage current.

The Effects of Cu Dopant on the Microstructure and Non-Ohmic Electrical Properties of ZnO Varistors

2011 ◽  
Vol 343-344 ◽  
pp. 160-165 ◽  
Author(s):  
Ji Wei Fan ◽  
Xiao Peng Li ◽  
Zhen Guo Zhang ◽  
Zhi Qiang Jiao ◽  
Xiang Yang Liu ◽  
...  
Keyword(s):  
Electrical Property ◽  
Electrical Properties ◽  
Grain Boundary ◽  
Grain Growth ◽  
Electrical Characteristics ◽  
Doping Effects ◽  
Zno Varistors ◽  
Doped Zno ◽  
Cu Dopant ◽  
Good Agreement

The doping effects of Cu on the microstructure and non-ohmic electrical properties of ZnO varistors were studied. Addition of Cu2O can enhance the ZnO grain growth during sintering. The SEM and EDS results revealed that the added Cu mainly distributed in the grain boundary and spinel phases of ZnO varistors. The Cu2O addition increased the both of grain and grain boundary resistances. However it decreased the non-ohmic electrical characteristics of ZnO varistors, which is a good agreement with similar findings on Ag2O additions, but contrasts to the reports of good non-ohmic electrical property which found on binary Cu doped ZnO varistors.

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

2011 ◽  
Vol 131 (3) ◽  
pp. 211-218
Author(s):  
Ai Fukumori ◽  
Takayuki Watanabe ◽  
Yuuki Sato ◽  
Shinzo Yoshikado
Keyword(s):  
Grain Growth ◽  
Electrical Characteristics ◽  
Zno Varistors

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.

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