Preparation of low voltage ZnO Varistor using point seed

A novel fabricated technique, by feeding two sets of different ZnO formulations powder in a die by parts, molded only once to produce layered structure(including layer A and layer B) low-voltage ZnO varistor. The samples are examined by using energy dispersive X-ray spectroscopy (EDS), electron probe microanalysis (EPMA), scanning electron microscope (SEM) and DC electrical measurements. EDS and EPMA data indicate that doped elements only exists in layer A, The results of SEM indicate that secondary phases are formed at grain boundaries in layer A, not found in layer B. It is found that the electrical properties of low-voltage varistor are improved without reducing thickness and changing energy absorption capabilities. The higher nonlinearity coefficients, lower breakdown fields and leakage currents of layered structure low-voltage ZnO varistor, as compared to those of ZnO varistor fabricated from the conventional route. The improved current-voltage properties are attributed to the band structure difference in both sides grains, due to the different ion concentration and species in both sides of grain boundary. Layered structure varistor also has more simpler prepared technology than multilayer chip varistor.

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Exaggerated Grain Growth of ZnO in Low Voltage ZnO Varistor.

Journal of the Japan Society of Powder and Powder Metallurgy ◽

10.2497/jjspm.41.193 ◽

1994 ◽

Vol 41 (2) ◽

pp. 193-195

Author(s):

Atsushi Iga ◽

Masahiro Ito ◽

Hideyuki Okinaka

Keyword(s):

Grain Growth ◽

Low Voltage ◽

Zno Varistor

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Interface states and MWS polarization contributions to the dielectric response of low voltage ZnO varistor

Ceramics International ◽

10.1016/j.ceramint.2010.08.036 ◽

2011 ◽

Vol 37 (1) ◽

pp. 207-214 ◽

Cited By ~ 16

Author(s):

C. Tsonos ◽

A. Kanapitsas ◽

D. Triantis ◽

C. Anastasiadis ◽

I. Stavrakas ◽

...

Keyword(s):

Dielectric Response ◽

Low Voltage ◽

Interface States ◽

Zno Varistor

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Micro-Degradation Characteristics and Mechanism of ZnO Varistors under Multi-Pulse Lightning Strike

Energies ◽

10.3390/en13102620 ◽

2020 ◽

Vol 13 (10) ◽

pp. 2620

Author(s):

Chunlong Zhang ◽

Hongyan Xing ◽

Chunying Li ◽

Ran Cai ◽

Dongbo Lv

Keyword(s):

Boundary Layer ◽

Grain Boundary ◽

Distribution Systems ◽

Pulse Current ◽

Low Voltage ◽

Grain Structure ◽

Lightning Strike ◽

Time Interval ◽

Zno Varistor ◽

Zno Varistors

In view of the problem that ZnO varistors are often subjected to thermal breakdown and deterioration due to lightning strikes in low-voltage power distribution systems, this article used a 8/20 µs multi-pulse surge current with a pulse time interval of 50 ms to perform shock experiments on ZnO varistors. SEM scanning electron microscope and an XRD diffractometer were used to analyze the structure of the grain boundary layer and the change of the crystalline phase material of ZnO varistor under the action of a multi-pulse current. The damage mechanism of ZnO varistor under the multi-pulse current was studied at the micro level. The results show that the average impact life of different types of ZnO varistor is significantly different. It was found that the types of trace elements and grain size in the grain boundary layer will affect the ability of ZnO varistor to withstand multi-pulse current. As the number of impulses increases, the grain structure of the ZnO varistor continues to degenerate. The unevenness of internal ion migration and the nonuniformity of the micro-grain boundary layer cause the local energy density to be too large and cause the local temperature rise to be too high, which eventually causes the internal grain boundary to melt through, and the local high temperature may cause the Bi element in the ZnO varistor to change in different crystal phases.

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Low-voltage ZnO varistor fabricated by the solution-coating method

Ceramics International ◽

10.1016/j.ceramint.2007.05.012 ◽

2008 ◽

Vol 34 (7) ◽

pp. 1697-1701 ◽

Cited By ~ 44

Author(s):

Q. Wang ◽

Y. Qin ◽

G.J. Xu ◽

L. Chen ◽

Y. Li ◽

...

Keyword(s):

Low Voltage ◽

Zno Varistor ◽

Coating Method

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Nonlinearity Characteristics of Low-Voltage Barium Titanate Based Zinc Oxide Varistor Ceramics Modified by Cobalt Dopants

Journal of Integrated Circuits and Systems ◽

10.29292/jics.v16i1.220 ◽

2021 ◽

Vol 16 (1) ◽

pp. 1-7

Author(s):

Shaifudin Muhamad Syaizwadi ◽

Mohd Sabri Mohd Ghazali ◽

Wan Mohamad Kamaruzzaman Wan Mohamad Ikhmal ◽

Mohd Anuar Muhamad Syahmi Hazim ◽

Wan Abdullah Wan Rafizah ◽

...

Keyword(s):

Barium Titanate ◽

Barrier Height ◽

Low Voltage ◽

Nonlinear Coefficient ◽

Solid State Reaction Method ◽

Zno Varistor ◽

Low Leakage ◽

Low Leakage Current ◽

Voltage Limit ◽

Zinc Oxide Varistor

Application of ZnO varistor at low voltage has increased significantly due to the high demands of low-voltage electronics with high nonlinearity characteristics and low leakage current. The varistor ceramics were developed via solid-state reaction method and the resultant sample was analyzed by means of SEM, EDS and XRD. The nonlinearity characteristics of ZnO varistor ceramics for different contents of cobalt oxide (Co3O4) at a given barium titanate (BaTiO3) amount were analyzed based on the J-E characteristics measurement. The increased value of nonlinear coefficient (α) equal to 4.8 was exhibited by the sample made with 12 wt.% BaTiO3 additive. As the concentration of dopant (Co3O4) incorporated was increased from 0.5 to 1.5 wt.%, the varistor voltage limit decreased from 8.9 V/mm to 7.0 V/mm, respectively. Additionally, the barrier height increased from 0.88 to 0.98 eV for 0.0 wt.% to 1.0 wt.% of Co3O4 concentration, respectively. The highest α of 7.2 was obtained at 0.5 wt.% Co3O4 and decreased with further doping content due to to the reduction of barrier height caused by the variation of electronic state at the grain boundaries.

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