Effect of MnO2 addition on microstructure and electrical properties of ZnO–V2O5-based varistor ceramics

Nahm, Choon-Woo

doi:10.1016/j.ceramint.2008.01.010

Cited by 48 publications

(20 citation statements)

References 12 publications

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“…(2) When a ZnO-Pr 6 O 11 varistor is doped with a certain amount of Nd [18] or La [47,48,50], or a ZnO-Bi 2 O 3 varistor is doped with a certain amount of Ho [23], it will produce an effect as illustrated in Fig. 2(b).…”

Section: Re Doping Effect On Nonlinear Coefficient Of Zno Varistorsmentioning

confidence: 99%

“…help to enhance the donor concentration, resulting in lower barrier height, and thus reducing the nonlinear coefficient of ZnO varistors [48,49].…”

Section: Re Doping Effect On Nonlinear Coefficient Of Zno Varistorsmentioning

confidence: 99%

“…3(a); Fig. 3(b) shows the effect of ZnO-Pr 6 O 11 varistors doped with Nd [18] or La [47,48,50], or a ZnO-Bi 2 O 3 varistor doped with Ho [23]; a ZnO-Pr 6 O 11 varistor doped with Tb can display an effect as illustrated in Fig. 3(c) [52,53]; and the effect of Ce doping into a ZnO-Bi 2 O 3 varistor can be illustrated in Fig.…”

Section: Journal Of Advanced Ceramicsmentioning

confidence: 99%

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Progress on rare-earth doped ZnO-based varistor materials

et al. 2013

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Rare-earth (RE) doping can greatly enhance the voltage gradient of ZnO-based varistors, and their nonlinear coefficient, leakage current, energy absorption capability, through-current capability and residual voltage can also be improved to certain extent. In this review, the progress on RE-doped ZnO-based varistor materials in recent years was summarized. The mechanism of RE doping on the electrical performance of ZnO varistors was analyzed. The issues in exploring new ZnO-based varistor materials by RE doping were indicated, and the development trends in this area were proposed.

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Section: Re Doping Effect On Nonlinear Coefficient Of Zno Varistorsmentioning

confidence: 99%

“…help to enhance the donor concentration, resulting in lower barrier height, and thus reducing the nonlinear coefficient of ZnO varistors [48,49].…”

Section: Re Doping Effect On Nonlinear Coefficient Of Zno Varistorsmentioning

confidence: 99%

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Progress on rare-earth doped ZnO-based varistor materials

et al. 2013

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“…The effects of the type and content of the other dopants on their microstructures and electrical properties have been systematically investigated, and the results demonstrate that MnO 2 is one of the most significant additives. The main second intergranular phase c-Zn 3 (VO 4 ) 2 , which is crucial to the electrical properties, can be stabilized to room temperature by the addition of Mn [4][5][6][7][8][9][10][11][12][13][14][15][16]. On the other hand, Mn ions can also exist in the ZnO grains interior to modify the electrical properties [5][6][7][8][9][10].…”

Section: Introductionmentioning

confidence: 99%

The AC impedance and variable temperature dielectric spectroscopic analysis of MnO2 doped and un-doped ZnO–V2O5 ceramics

et al. 2011

J Mater Sci: Mater Electron

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The electrical and dielectric properties of MnO 2 doped and un-doped ZnO-V 2 O 5 ceramics were studied by ac impedance and variable temperature dielectric spectroscopy. The results show that V and Mn ions simultaneously segregated at the grain boundaries to form an intergranular phase, increasing the resistivity of the intervening layer and the Schottky barrier at the grain boundaries, and then improving the varistor performance. An obvious loss peak appeared in all the samples, which means an effective depletion layer has formed. As for the samples sintered at 1,000°C for 2 h, the activation energy of the characteristic relaxation process is about 0.339 eV for 99.5 mol% ZnO ? 0.5 mol% V 2 O 5 and 0.352 eV for 99.0 mol% ZnO ? 0.5 mol% V 2 O 5 ? 0.5 mol% MnO 2 , respectively, which means this relaxation process is associated with oxygen vacancy V O Á .

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“…A study on ZnO-V 2 O 5 -based ceramics is in early stage in terms of ceramic composition and sintering process [10][11][12][13][14][15][16][17][18]. To develop useful ZnO-V 2 O 5 -based ceramics, as usual it is very important to investigate the effects of various additives on varistor properties.…”

Section: Introductionmentioning

confidence: 99%

Varistor Properties and Aging Behavior of ZnO-V₂O₅-MnO₂-Co₃O₄-La₂O₃Ceramics Modified with Various Additives (Cr, Nb, Dy, Bi)

Nahm¹,

Lee²,

Heo³

et al. 2013

Transactions on Electrical and Electronic Materials

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The effects of additives (Cr, Nb, Dy, and Bi) on microstructure, electrical properties, dielectric characteristics, and aging behavior of ZnO-V 2 O 5 -MnO 2 -Co 3 O 4 -La 2 O 3 (ZVMCL) ceramics were systematically investigated. The phase formed in common for all ZVMCL ceramics modified with various additives consisted of ZnO grain as a main phase, and Zn 3 (VO 4 ) 2 and ZnV 2 O 4 as the secondary phases. The sintered density and average grain size were in the range of 5.4-5.54 g/cm 3 and 3.7-5.1 μm, respectively. The ZVMCL ceramics modified with Cr exhibited the highest breakdown field (6,386 V/cm) and the ZVMCL ceramics modified with Nb exhibited the lowest breakdown field (3,517 V/cm). All additives enhanced the nonlinear coefficient (α), by a small or large margin, in particular, additives such as Bi and Nb noticeably increased the nonlinear coefficient, with α=25.5 and α=23, respectively. However, on the whole, all additives did not improve the stability against a DC stress, compared with ZVMCL ceramics.Keywords: Additives, Nonlinear properties, Aging behavior, ZnO-V 2 O 5 -based varistor ceramics Regular Paper INTRODUCTIONZnO is a versatile material that possesses a wide range of applications as active component in gas sensors, optical devices, grain boundary effect devices, etc. ZnO varistors are typical semiconducting electro-ceramic devices, which exhibit a nonlinear V-I relation due to the grain boundary effect formed by sintering ZnO powder with minor additives [1]. The sintering process gives rise to a microstructure, which consists of semiconducting n-type ZnO grains surrounded by very thin insulating intergranular layers. Each ZnO grain acts as if it has a semiconductor junction at the grain boundary [2,3]. Since nonlinear electrical behavior occurs like back-to-back zener diode at each boundary, the impurity doped ZnO varistors can be considered as a multi-junction device composed of many series and parallel connection of grain boundaries [2,3]. The grain size distribution plays a major role in electrical behavior. Electrically, ZnO varistors exhibit highly nonlinear voltage-current (V-I) properties expressed by the relation I = CV α , where I is the current, V is the voltage, C is a constant, α is the nonlinear coefficient, which characterizes the nonlinear properties of the varistors [4,5].ZnO ceramics cannot exhibit a varistor behavior without adding heavy elements with large ionic radii such as Bi, Pr, Ba, etc. Commercial ZnO-Bi 2 O 3 -based ceramics and ZnO-Pr 6 O 11 -based ceramics cannot be co-fired with a silver inner-electrode (m.p. 961℃) in multilayered chip varistors because of the relatively high sintering temperature above 1,000℃ [6,7]. Therefore, new varistor ceramics are required in order to use a silver innerelectrode. Among the various ceramics, one candidate is the ZnO-V 2 O 5 ceramics [8,9]. This system can be sintered at a rela-

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Effect of MnO2 addition on microstructure and electrical properties of ZnO–V2O5-based varistor ceramics

Cited by 48 publications

References 12 publications

Progress on rare-earth doped ZnO-based varistor materials

Progress on rare-earth doped ZnO-based varistor materials

The AC impedance and variable temperature dielectric spectroscopic analysis of MnO2 doped and un-doped ZnO–V2O5 ceramics

Varistor Properties and Aging Behavior of ZnO-V₂O₅-MnO₂-Co₃O₄-La₂O₃Ceramics Modified with Various Additives (Cr, Nb, Dy, Bi)

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Effect of MnO2 addition on microstructure and electrical properties of ZnO–V2O5-based varistor ceramics

Cited by 48 publications

References 12 publications

Progress on rare-earth doped ZnO-based varistor materials

Progress on rare-earth doped ZnO-based varistor materials

The AC impedance and variable temperature dielectric spectroscopic analysis of MnO2 doped and un-doped ZnO–V2O5 ceramics

Varistor Properties and Aging Behavior of ZnO-V2O5-MnO2-Co3O4-La2O3Ceramics Modified with Various Additives (Cr, Nb, Dy, Bi)

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Varistor Properties and Aging Behavior of ZnO-V₂O₅-MnO₂-Co₃O₄-La₂O₃Ceramics Modified with Various Additives (Cr, Nb, Dy, Bi)