Key role of oxygen at zinc oxide varistor grain boundaries

Stucki, F.; Greuter, F.

doi:10.1063/1.103661

Cited by 181 publications

(103 citation statements)

References 9 publications

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“…32,33 However, the microscopic origins of DSB are still un-fully identified, 32 though various models have been proposed focusing on the conduction mechanism since the discovery of non-ohmic properties of ZnO varistors by Matsuoka, 34 including the successful description by Pike, Blatter and Greuter. 1,33,35,36 So far, the intergranular layer, 34 segregation of additives, 37,38 thin disordered layer, 39 oxygen-excess defects like chemisorbed oxygen or excess amount of oxygen, 40,41 native point defects such as zinc vacancy (V Zn ) and oxygen interstitial (O i ), 2,15,42 and certain complex defect composed of additives and native defects 43 have all been considered as the possible candidates for promoting the generation of acceptor-states. In effect, recent successes in performing first-principles calculations on ZnO materials to consider the grain boundary structure, 2,32 dopant segregation 44 and defect formation [43][44][45] have made it possible to understand the formation of acceptor state from atomic scale.…”

Section: A Formation Of Double-schottky Barriermentioning

confidence: 99%

Electrical degradation of double-Schottky barrier in ZnO varistors

Cheng

2016

AIP Advances

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Researches on electrical degradation of double-Schottky barrier in ZnO varistors are reviewed, aimed at the constitution of a full picture of universal degradation mechanism within the perspective of defect. Recent advances in study of ZnO materials by atomic-scale first-principles calculations are partly included and discussed, which brings to our attention distinct cognition on the native point defects and their profound impact on degradation.

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Section: A Formation Of Double-schottky Barriermentioning

confidence: 99%

Electrical degradation of double-Schottky barrier in ZnO varistors

Cheng

2016

AIP Advances

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“…7,13) This is consistent with experimental reports that nonlinear characteristics strongly depend on oxygen partial pressure during heat treatment and sintering processes, 14,15) and that oxygen accumulation is more abundant at intergranular-fractured surfaces in untreated samples than in electrically degraded samples. 16,17) The excessive oxygen at interface regions may be regarded as segregation of native defects associated with oxygen excess such as Zn vacancies and O interstitials.…”

Section: Introductionmentioning

confidence: 99%

First-Principles Calculations of Co Impurities and Native Defects in ZnO

et al. 2002

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First-principles plane-wave pseudopotential calculations have been conducted to investigate Co impurities and native defects associated with oxygen excess in ZnO. The electronic states and formation energies are evaluated using the total energies of supercells. The electronic states indicate that Co impurities are donor-like, while native defects associated with oxygen excess are acceptor-like. Among the native defects, Zn vacancies are likely to be a dominant species in view of the much lower formation energy than those of the others. Calculations for Co impurity-Zn vacancy complexes imply that Co impurities stabilize Zn vacancies and hence oxygen excess in their vicinities. This is suggested to be a role of Co impurities at grain boundaries in ZnO varistor ceramics.

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“…However, it is well known that the electrical properties of this and other electroceramic materials can be controlled by the incorporation of dopants which have a tendency to segregate to the grain boundaries [67][68][69][70][71][72][73][74][75][76], While the techniques described in this paper are not capable of observing individual vacancies, they are capable of observing the presence of dopant atoms of the order of 1-2 atoms per atomic column. This is simply due to the nature of the techniques.…”

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confidence: 99%

Direct experimental determination of the atomic structure at internal interfaces

Browning

Pennycook

1996

J. Phys. D: Appl. Phys.

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A crucial first step in understanding the effect that internal interfaces have on the properties of materials is the ability to determine the atomic structure at the interface. As interfaces can contain atomic disorder, dislocations, segregated impurities and interphases, sensitivity to all of these features is essential for complete experimental characterization. By combining Z-contrast imaging and electron energy loss spectroscopy (EELS) in a dedicated scanning transmission electron microscope (STEM), the ability to probe the structure, bonding and composition at interfaces with the necessary atomic resolution has been obtained. Experimental conditions can be controlled to provide, simultaneously, both incoherent imaging and spectroscopy. This enables interface structures observed in the image to be interpreted intuitively and the bonding in a specified atomic column to be probed directly by EELS. The bonding and structure information can then be correlated using bond-valence sum analysis to produce structural models. This technique is demonstrated for 25", 36" and 67" symmetric and 45" and 25" asymmetric [Ool] tilt grain boundaries in SrTiO,. The structures of both types of boundary were found to contain partially occupied columns in the boundary plane. From these experimental results, a series of structural units were identified which could be combined, using continuity of grain boundary structure principles, to construct all [Ool] tilt boundaries in SrTiO,. Using these models, the ability of this technique to address the issues of vacancies and dopant segregation at grain boundaries in electroceramics is discussed. %e submitted manuscript has been authored by a contractor of the U.S.

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Key role of oxygen at zinc oxide varistor grain boundaries

Abstract: Complex plane analysis of trapping phenomena in zinc oxide based varistor grain boundaries

Cited by 181 publications

References 9 publications

Electrical degradation of double-Schottky barrier in ZnO varistors

Electrical degradation of double-Schottky barrier in ZnO varistors

First-Principles Calculations of Co Impurities and Native Defects in ZnO

Direct experimental determination of the atomic structure at internal interfaces

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