Grain-Boundary Resistance and Nonlinear Coefficient Correlation for SnO2-Based Varistors

Masteghin, Mateus G.; Orlandi, Marcelo Ornaghi

doi:10.1590/1980-5373-mr-2016-0210

Cited by 20 publications

(7 citation statements)

References 24 publications

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“…Because varistor consists of a high resistance (or high potential barrier) grain boundary phase with a highly conductive grain, such a structure can be simulated by an equivalent circuit with a variable resistor for the grain boundary and a parallel circuit of a capacitor and an inductor for the conductive grain in series. 26 Circuit simulation (Multisim, NI), based on the change of resistance observed in Figure 7, on a circuit equivalent to the present setup qualitatively shows how changes in resistance impact the PSN output, which can subsequently impact the waveform response. This simulation replicates the slowdown of the voltage ramp rate due to the decreasing resistance with rising temperature.…”

Section: Changes In Resistance and Regulating Voltagementioning

confidence: 76%

High‐voltage surge protection by a varistor‐filled air gap

et al. 2021

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The electric discharge across a varistor granule filled air gap under a fast-rising voltage pulse was investigated for surge protection applications. The effects of temperature and pressure on the arc and the electrical conduction were analyzed by the characteristic changes in voltage waveforms triggered by a fast-rising high voltage pulse.In addition to the gap size, experimental results show that competing mechanisms among arc conduction, conduction through the varistor granule network, thermionic emission from Joule heating at granule-to-granule contact points, and the magnitude of the switching voltage dictate the maximum surge protection voltage for the filled air gap. Experimental evidence indicated that accumulated degradation was created at small contact points between varistor granules by repetitive assaults from longer duration, high voltage pulses. The uniqueness of using varistor over other dielectric granules in an air gap for surge protection is identified and discussed.

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Section: Changes In Resistance and Regulating Voltagementioning

confidence: 76%

High‐voltage surge protection by a varistor‐filled air gap

et al. 2021

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“…For example, the image correlation method [22,23] is widely applied now. There is also a precise technique based on the triple points of grain boundaries [24,25] which can be followed by an electron backscatter diffraction (EBSD) method [26]. However, these methods have significant limitations (difficult sample preparation, requirement of conductive coatings, stability of electron beam for best data acquisition, etc.).…”

Section: Motivation and Aimsmentioning

confidence: 99%

On the Applicability of Stereological Methods for the Modelling of a Local Plastic Deformation in Grained Structure: Mathematical Principles

Minárik

Martinkovič

2020

Crystals

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Analysis of systems and structures from their cross-sectional images finds applications in many branches. Therefore, the question of content, quantity, and accuracy of information obtained from various techniques based on cross-sectional views of structures is particularly important. Application of conventional techniques for two-dimensional imaging on the analysis of structure from a cross-sectional image is limited. The reason for this limitation is the fact that these techniques use a fixed cross-sectional plane and therefore cannot check the 3D structural changes caused by deformation. Geometric orientation of a grained structure must be considered when data, scanned from a cross section, is processed in order to obtain information about local deformation in this structure. The so-called degree of structure orientation in 3D can be estimated experimentally from the cross-sectional image of the structure by the statistical (Saltykov) method of oriented testing lines. Subsequently if the correlation between orientation and deformation were to be known a detailed map of local deformation in the structure could be revealed. Unfortunately, exact theoretical works dealing with the assessment of local deformation by means of change of structure orientation in 3D are still missing. Our work seeks to partially remove this shortcoming. In our work we are interested in how the transformation of the image of a grained structure in a cross-sectional plane reflects structure deformation. An initial shape of grains is assumed which is transformed into a deformed shape by analytic calculation. We present brief mathematical derivations aimed at the problem of single grain-surface area deformation. The main goal of this work led to the design of a computationally low consuming procedure for quantification of local deformation in a grained structure based on the distortion of the image of this structure in a cross-sectional view.

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“…Pianaro et al [10] reported to have obtained a nonlinear coefficient (α) of 8 and a breakdown electric field (E b ) of 1870 V cm −1 after conducting a detailed investigation on SnO 2 -CoO-Nb 2 O 5 varistor system. Orlandi et al [14] and Masteghin et al [15] also showed that the SnO 2 -MnO 2 -Nb 2 O 5 system can present a nonlinear coefficient (α) of 11 with a breakdown electric field (E b ) of 8786 V cm −1 .…”

Section: Introductionmentioning

confidence: 99%

High-performance and low-voltage SnO2-based varistors

Masteghin

Bertinotti

Orlandi

2017

Ceramics International

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This paper presents the results of a thorough study conducted on the action mechanism of one-dimensional single-crystalline SnO 2 nanobelts in decreasing the breakdown electric field (E b) in SnO 2-based varistors. The proposed method has general validity in that our investigation was focused on the traditional varistor composition SnO 2-CoO-Cr 2 O 3-Nb 2 O 5. To accomplish our study objective, two methods of decreasing E b value were compared; one involving the increase in average grain size of the varistor through the sintering time and the other one related to the addition of nanobelts. The morphological results show that the method involving the increase in average grain size is limited by the formation of intragranular pores. Furthermore, despite contributing successfully towards decreasing the E b value (which underwent a decline from 3990 V cm −1 to 1133 V cm −1 with an increase in sintering time from 1 h to 2 h), the reduction obtained by this method is found to be much lower compared to that obtained via the nanobelts insertion method (E b = 270 V cm −1). Impedance spectroscopy results showed that the insertion of nanobelts caused a decline in the grain boundary resistance while surface potential measurements proved that this decline in resistance is attributed to the absence of potential barriers along the belts which leads to the formation of a lower resistance percolation path in the varistor.

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Grain-Boundary Resistance and Nonlinear Coefficient Correlation for SnO2-Based Varistors

Cited by 20 publications

References 24 publications

High‐voltage surge protection by a varistor‐filled air gap

High‐voltage surge protection by a varistor‐filled air gap

On the Applicability of Stereological Methods for the Modelling of a Local Plastic Deformation in Grained Structure: Mathematical Principles

High-performance and low-voltage SnO2-based varistors

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