The control of abnormal grain growth in low-voltage SnO2 varistors by microseed addition

Shahraki, Mohammad Maleki; Golmohammad, Mohammad; Safaee, Iman; Chermahini, Mehdi Delshad

doi:10.1016/j.ceramint.2017.11.129

Cited by 15 publications

(7 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Thus, AGG studies remain an area of active research with an emphasis on electrical steels [9][10][11]. Furthermore, recent investigations deal with AGG during sintering [33][34][35][36] where, however, porosity plays a critical role [37]. Other studies consider the role of local plastic strain on the formation of abnormal grains [24,38,39].…”

Section: Introductionmentioning

confidence: 99%

Phase Field Modelling of Abnormal Grain Growth

2019

View full text Add to dashboard Cite

Heterogeneous grain structures may develop due to abnormal grain growth during processing of polycrystalline materials ranging from metals and alloys to ceramics. The phenomenon must be controlled in practical applications where typically homogeneous grain structures are desired. Recent advances in experimental and computational techniques have, thus, stimulated the need to revisit the underlying growth mechanisms. Here, phase field modelling is used to systematically evaluate conditions for initiation of abnormal grain growth. Grain boundaries are classified into two classes, i.e., high- and low-mobility boundaries. Three different approaches are considered for having high- and low-mobility boundaries: (i) critical threshold angle of grain boundary disorientation above which boundaries are highly mobile, (ii) two grain types A and B with the A–B boundaries being highly mobile, and (iii) three grain types, A, B and C with the A–B boundaries being fast. For these different scenarios, 2D simulations have been performed to quantify the effect of variations in the mobility ratio, threshold angle and fractions of grain types, respectively, on the potential onset of abnormal grain growth and the degree of heterogeneity in the resulting grain structures. The required mobility ratios to observe abnormal grain growth are quantified as a function of the fraction of high-mobility boundaries. The scenario with three grain types (A, B, C) has been identified as one that promotes strongly irregular abnormal grains including island grains, as observed experimentally.

show abstract

Section: Introductionmentioning

confidence: 99%

Phase Field Modelling of Abnormal Grain Growth

2019

View full text Add to dashboard Cite

show abstract

“…During the last few years, a new branch of electroceramics that involves nanotechnology has emerged [12,13]. This not only enables the possibility of fabricating more complex and advanced devices, but it also improves the features of the actual materials and their processing.…”

Section: Introductionmentioning

confidence: 99%

“…This not only enables the possibility of fabricating more complex and advanced devices, but it also improves the features of the actual materials and their processing. In particular, for SnO 2 based varistors, a growing body of literature has been published reporting results of nanostructured precursors used to enhance densification [12][13][14]. This work aims to evaluate and compare the performance of the micro and nanoparticles of Co 3 O 4 as a densifier dopant.…”

Section: Introductionmentioning

confidence: 99%

A comparative study between the addition of nano and micro-particles of Co3O4 on the electrical and microstructural properties of a ceramic system based on SnO2

et al. 2019

View full text Add to dashboard Cite

A comparative study between the addition of Co3O4 micro-particles and nano-particles as densifying dopant of a SnO2 based varistor system was conducted. The ceramic composition was (99.9-X) %SnO2–X %Co3O4–0.05 %Cr2O3–0.05 %Nb2O5 where X = 0, 0.5, 1.0, 2.0 and 4.0 mol%. Two particle sizes of Co3O4 were used (~5 µm and ~50 nm). The addition of 0.5 mol% of Co3O4 nano-particles promoted an increase of grain size of sintered samples up to 7.9 µm, that is, the maximum value among all variations. Characterization techniques such as TGA, DTA, XRD, and Rietveld analysis revealed a decrease of 16 ºC in the formation temperature of Co2SnO4 as well as an increase of 2.6 wt% in the amount of said phase with the use of 4.0 mol% of Co3O4 nano-particles in comparison with micro-particles. Statistical analysis indicated that the addition of nano-particles of Co3O4 yield better repeatability on densification of ceramic samples. Residual porosity also was decreased. Electrical breakdown and non-linear coefficient values correspond to a non-ohmic behavior with potential application on manufacture of high voltage varistors. The findings of this work can be used as a reference for conducting a later study to improve the electrical properties or even to lower the sintering temperature.

show abstract

“…It is well established that there is a close relationship between microstructure and electrical properties in polycrystalline electroceramics, especially in varistors [1][2][3][4][5][6] -a special class of ceramics presenting a nonlinear relationship between the applied potential and the resulting current [7]. When dealing with varistors, the grain size distribution has a major role determining the breakdown electric field (E b ), i.e., the point at which a small change in the applied voltage generates a large variation in the current passing through the device.…”

Section: Introductionmentioning

confidence: 99%

Coalescence growth mechanism of inserted tin dioxide belts in polycrystalline SnO2-based ceramics

Masteghin

Bertinotti

Orlandi

2018

Materials Characterization

View full text Add to dashboard Cite

SnO 2-based varistors have been considered promising technological devices. However their practical application is usually stated as limited to high voltage circuits based on the high breakdown electric field exhibited by these ceramics. Recently, authors have shown that the insertion of one-dimensional (1D) SnO 2 belts allows overcoming this limitation. In this work, we present a detailed study of the growth mechanism of the belts inside varistors using electron microscopy techniques. We were able to show that mass transport has an intrinsic dependence on the sintering time and requires similar crystalline structure between the belts and the matrix. Dual beam and high-resolution transmission electron microscopy techniques permitted determining that 3D growth of belts occurs by coalescence.

show abstract

The control of abnormal grain growth in low-voltage SnO2 varistors by microseed addition

Cited by 15 publications

References 23 publications

Phase Field Modelling of Abnormal Grain Growth

Phase Field Modelling of Abnormal Grain Growth

A comparative study between the addition of nano and micro-particles of Co3O4 on the electrical and microstructural properties of a ceramic system based on SnO2

Coalescence growth mechanism of inserted tin dioxide belts in polycrystalline SnO2-based ceramics

Contact Info

Product

Resources

About