Microstructure–Property Relationships for Low‐Voltage Varistors

Pan, Wen-Hsuan; Kuo, Shu-Ting; Tuan, Wei‐Hsing; Chen, Huey-Ru

doi:10.1111/j.1744-7402.2009.02429.x

Cited by 12 publications

(11 citation statements)

References 22 publications

(50 reference statements)

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“…For instance, battery powered and mobile appliances require protection from transient voltage of between 4 to 20 V (dc voltage) while many communication devices need fast response protection from transient voltage of 22 –68.V [1–3]. These factors create needs for continuous development of ZnO varistor materials with fast response, highly non-linear current-voltage characteristics and energy absorption capabilities at low breakdown voltage.…”

Section: Introductionmentioning

confidence: 99%

Synthesis Mechanism of Low-Voltage Praseodymium Oxide Doped Zinc Oxide Varistor Ceramics Prepared Through Modified Citrate Gel Coating

Abdullah

Zakaria

Ghazali

2012

IJMS

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High demands on low-voltage electronics have increased the need for zinc oxide (ZnO) varistors with fast response, highly non-linear current-voltage characteristics and energy absorption capabilities at low breakdown voltage. However, trade-off between breakdown voltage and grain size poses a critical bottle-neck in the production of low-voltage varistors. The present study highlights the synthesis mechanism for obtaining praseodymium oxide (Pr6O11) based ZnO varistor ceramics having breakdown voltages of 2.8 to 13.3 V/mm through employment of direct modified citrate gel coating technique. Precursor powder and its ceramics were examined by means of TG/DTG, FTIR, XRD and FESEM analyses. The electrical properties as a function of Pr6O11 addition were analyzed on the basis of I-V characteristic measurement. The breakdown voltage could be adjusted from 0.01 to 0.06 V per grain boundary by controlling the amount of Pr6O11 from 0.2 to 0.8 mol%, without alteration of the grain size. The non-linearity coefficient, α, varied from 3.0 to 3.5 and the barrier height ranged from 0.56 to 0.64 eV. Breakdown voltage and α lowering with increasing Pr6O11 content were associated to reduction in the barrier height caused by variation in O vacancies at grain boundary.

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Section: Introductionmentioning

confidence: 99%

Synthesis Mechanism of Low-Voltage Praseodymium Oxide Doped Zinc Oxide Varistor Ceramics Prepared Through Modified Citrate Gel Coating

Abdullah

Zakaria

Ghazali

2012

IJMS

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“…Generally, application of ceramic layers with an enhanced thickness leads to an increase of the number of grain boundaries and consequently to a higher breakdown voltage. However, this effect can be to some extent suppressed by facilitated grain growth due to a larger space between internal electrodes [27]. In this work, it was stated that both the breakdown voltage and the nonlinear coefficient are higher when the thickness of the varistor layers is increased.…”

Section: Resultsmentioning

confidence: 91%

“…Lower values of the breakdown voltage for the varistors sintered at higher temperatures are due to the grain growth and consequently a decrease in the grain boundary number between the adjacent electrodes. The electrostatic barrier created at Bi-rich boundaries of ZnO grains was estimated to be at a level of about 3 V [2,27]. The breakdown voltage of a multilayer varistor increases linearly with increasing number of grain boundaries between inner electrodes [27].…”

Section: Resultsmentioning

confidence: 99%

“…The electrostatic barrier created at Bi-rich boundaries of ZnO grains was estimated to be at a level of about 3 V [2,27]. The breakdown voltage of a multilayer varistor increases linearly with increasing number of grain boundaries between inner electrodes [27]. Generally, application of ceramic layers with an enhanced thickness leads to an increase of the number of grain boundaries and consequently to a higher breakdown voltage.…”

Section: Resultsmentioning

confidence: 99%

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Influence of processing on microstructure and electrical characteristics of multilayer varistors

2019

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The paper reports on the influence of processing on microstructure and electrical properties of multilayer varistors based on zinc oxide doped with Bi 2 O 3 , Sb 2 O 3 , Co 2 O 3 , MnO, Cr 2 O 3 , B 2 O 3 , and SiO 2. 0.5-1 wt% of AlF 3-CaB 4 O 7 was used as a new effective sintering aid. The behavior of green laminates during heating was characterized using differential thermal analysis and a heating microscope. As revealed by XRD, SEM, and EDS methods, the varistor layers are composed of ZnO grains of 1-5 μm size, submicrometer spinel and pyrochlore grains situated at the ZnO grain boundaries, and nanometric Bi 2 O 3-rich films surrounding ZnO grains. Complex impedance studies carried out in the frequency range of 0.01 Hz-2 MHz at temperatures changing from-30 to 150 ℃ imply the formation of semiconducting grains and insulating grain boundaries. Frequency dependence of dielectric permittivity shows a high plateau at lower frequencies, typical for barrier layer capacitance effect. The fabricated multilayer varistors show nonlinear current-voltage characteristics with a high nonlinear coefficient of 26-38. The breakdown voltage was found to decrease within the range of 66-130 V with sintering temperature increasing from 1000 to 1100 ℃. Good surge current capability of the varistors was confirmed by the tests using 8/20 μs pulses.

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“…The development of ZnO varistors at low breakdown voltage reduced the ZnO grains and grain boundaries within the structure. However, the most critical problem for low-voltage varistor production lies within the variation of grain size distribution [5].…”

Section: Introductionmentioning

confidence: 99%

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

Shaifudin¹,

Ghazali

Ikhmal³

et al. 2021

JICS

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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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Microstructure–Property Relationships for Low‐Voltage Varistors

Cited by 12 publications

References 22 publications

Synthesis Mechanism of Low-Voltage Praseodymium Oxide Doped Zinc Oxide Varistor Ceramics Prepared Through Modified Citrate Gel Coating

Synthesis Mechanism of Low-Voltage Praseodymium Oxide Doped Zinc Oxide Varistor Ceramics Prepared Through Modified Citrate Gel Coating

Influence of processing on microstructure and electrical characteristics of multilayer varistors

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

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