Effect of the addition of ZnO seeds on the electrical proprieties of ZnO-based varistors

Souza, Flávio L.; Gomes, J. W.; Bueno, Paulo Roberto; Cassia-Santos, M. R.; Araujo, A. L.; Leite, E. R.; Longo, Elson; Varela, José Arana

doi:10.1016/s0254-0584(03)00083-x

Cited by 35 publications

(26 citation statements)

References 10 publications

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“…The most classical ways of making low-voltage varistors are through grain coarsening techniques by making varistor from crushed ceramics, prolonged sintering processes at higher temperatures and adding grain growth enhancers such as TiO 2 [7]. Other ways include employment of seeding technique by using grown ZnO crystal seeds as precursor [8–10] and deposition technique to fabricate multilayered thin film varistors with interdigitated electrodes [11]. Grain coarsening and seeding techniques could be economically less feasible as they are energy intensive processes and suffer from inhomogeneous microstructure which leads to inconsistent current-voltage characteristics [8].…”

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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“…Several theoretical studies and some scanning probe technical studies are found in the literature and can be used to quantify the interfacial properties associated whit local transport properties, grain boundaries, or potential barrier; there are also some references that associate these properties with different dopants 2–5,9–13,17,24–27,34,42–44 . Shao et al 43 made an important contribution by analyzing the grain boundary behavior in a commercial polycrystalline ZnO using a nanoimpedance microscopy/spectroscopy technique that is based on impedance spectroscopy with a conductive AFM tip.…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the main feature of these systems is the presence of grains connected at their interfaces. This is considered a determining factor of the systems' electrical properties, i.e., their stability after a transient voltage surge is directly related to the stability of the electrical barriers in the grain boundaries 3,4,9,17 . This stability is affected by the choice of dopants, and it is also conditioned to the uniformity of the dopants' distribution at the grain boundaries and to the chemistry at the boundaries.…”

Section: Introductionmentioning

confidence: 99%

“…ZnO varistor ceramics have a highly complex structure, which makes it difficult to control their morphology and electrical characteristics. The main factor for the success of the technology is the discovery of various dopants that impart the desired electrical properties to ZnO, while also allowing for the necessary microstructural control 3,9–18 …”

Section: Introductionmentioning

confidence: 99%

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An AFM/EFM Study of the Grain Boundary in ZnO‐Based Varistor Materials

Gheno

Kiminami

Morelli

et al. 2008

Journal of the American Ceramic Society

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Zinc oxide (ZnO)‐based varistors are metal oxide varistors whose nonlinear properties are characterized by electrical resistance that decreases as the applied field increases. The multiphasic nature of varistors leads to the formation of Schottky barriers, which are responsible for the materials' nonlinear behavior. The objective of this work was to image the potential barriers in ZnO doped with 0.5 mol% Cu and x wt% G (G is a frit and x=0, 1, and 5 wt%). The frit served to form a glassy insulating layer around the grain boundaries. Samples were sintered at 1050°C and the microstructures were analyzed using a Nanoscope IIIa atomic force microscope. The results of the electric force microscopy experiments map the electric field distribution on the surface of CuO–ZnO‐based ceramics.

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“…ZnO based varistors are fabricated with different type of additives which play an important role in its non-linear characteristics. Its unique grain boundary feature is responsible for non-linear current-voltage ( I – V ) characteristics of the device [1,2] and thus is used to protect electrical equipment against unwanted electrical surges. Currently, ZnO based varistors are being used for low-voltage applications.…”

Section: Introductionmentioning

confidence: 99%

Use of a Reflectance Spectroscopy Accessory for Optical Characterization of ZnO-Bi2O3-TiO2 Ceramics

Ghazali

Zakaria

Rizwan

et al. 2011

IJMS

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The optical band-gap energy (Eg) is an important feature of semiconductors which determines their applications in optoelectronics. Therefore, it is necessary to investigate the electronic states of ceramic ZnO and the effect of doped impurities under different processing conditions. Eg of the ceramic ZnO + xBi2O3 + xTiO2, where x = 0.5 mol%, was determined using a UV-Vis spectrophotometer attached to a Reflectance Spectroscopy Accessory for powdered samples. The samples was prepared using the solid-state route and sintered at temperatures from 1140 to 1260 °C for 45 and 90 minutes. Eg was observed to decrease with an increase of sintering temperature. XRD analysis indicated hexagonal ZnO and few small peaks of intergranular layers of secondary phases. The relative density of the sintered ceramics decreased and the average grain size increased with the increase of sintering temperature.

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Effect of the addition of ZnO seeds on the electrical proprieties of ZnO-based varistors

Cited by 35 publications

References 10 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

An AFM/EFM Study of the Grain Boundary in ZnO‐Based Varistor Materials

Use of a Reflectance Spectroscopy Accessory for Optical Characterization of ZnO-Bi2O3-TiO2 Ceramics

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