Grain growth in weak electric fields in strontium titanate: Grain growth acceleration by defect redistribution

Rheinheimer, Wolfgang; Fülling, Manuel; Hoffmann, Michael J.

doi:10.1016/j.jeurceramsoc.2016.04.033

Cited by 35 publications

(56 citation statements)

References 52 publications

(88 reference statements)

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“…The scattering in the data is because of the grain size in the polycrystal as evident in Figure B,C. A more detailed discussion of microstructures and scattering can be found elsewhere . However, the trendline (thick line in Figure A) and mean grain sizes show that no gradient in the microstructure is visible across the sample.…”

Section: Resultsmentioning

confidence: 91%

“…Samples were cut into discs of a thickness of 1 mm and polished (diamond slurry, 0.25 μm) and then scratched with a polishing disc (30 μm diamonds). These scratches constitute markers so that during diffusion‐bonding of the seeded polycrystals the original position of the interface is clear (Figure C).…”

Section: Methodsmentioning

confidence: 99%

“…To prevent a chemical reaction or bonding of the sample to the alumina rods of the load frame, a thin layer of coarse‐grained zirconia powder was placed between the sample and the alumina supports. Further details of this procedure are published elsewhere …”

Section: Methodsmentioning

confidence: 99%

“…The most simplified case is observing grain growth (ie, no shrinkage) in an electric field, but without electric power dissipation (ie, with blocking electrodes). This experiment was conducted in a previous study on strontium titanate, a material for which vast information is available on microstructure evolution in the absence of electric field, point‐defect chemistry, and interfacial properties . In this experiment, the seeded polycrystal technique was used.…”

Section: Introductionmentioning

confidence: 99%

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Grain growth in strontium titanate in electric fields: The impact of space‐charge on the grain‐boundary mobility

et al. 2018

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This study investigates grain growth in the perovskite oxide strontium titanate in an electric field. The seeded polycrystal technique was chosen as it provides a sensitive and controlled setup to evaluate the impact of different parameters on grain growth due to the well‐defined driving force for grain growth. Current blocking electrodes were used to prevent Joule heating. The results show faster grain growth, and thus, higher grain‐boundary mobility at the negative electrode. It is argued that the electric field causes point‐defect redistribution, resulting in a higher oxygen vacancy concentration at the negative electrode. The local oxygen vacancy concentration is suggested to affect the space‐charge potential at the grain boundaries. A thermodynamic treatment of the grain‐boundary potential at a grain boundary without field shows that for a high oxygen vacancy concentration less space‐charge and less accumulation of cationic defects to the boundary occurs. Therefore, at the negative electrode, a higher oxygen vacancy concentration results in less space‐charge and less accumulation of cationic defects. The lower degree of defect accumulation requires less diffusion of segregated defects during grain‐boundary migration, so that at the negative electrode faster grain growth is expected, as found in the experiments.

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Section: Resultsmentioning

confidence: 91%

Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Grain growth in strontium titanate in electric fields: The impact of space‐charge on the grain‐boundary mobility

et al. 2018

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“…Rheiheimer et al 28. recently conducted a model experiment to study the effect of weak electric fields on grain growth in strontium titanate.…”

Section: Discussionmentioning

confidence: 99%

On the Role of the Electrical Field in Spark Plasma Sintering of UO2+x

Tyrpekl

Naji

Holzhäuser

et al. 2017

Sci Rep

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The electric field has a large effect on the stoichiometry and grain growth of UO2+x during Spark Plasma Sintering. UO2+x is gradually reduced to UO2.00 as a function of sintering temperature and time. A gradient in the oxidation state within the pellets is observed in intermediate conditions. The shape of the gradient depends unequivocally on the direction of the electrical field. The positive surface of the pellet shows a higher oxidation state compared to the negative one. An area with larger grain size is found close to the positive electrode, but not in contact with it. We interpret these findings with the redistribution of defects under an electric field, which affect the stoichiometry of UO2+x and thus the cation diffusivity. The results bear implications for understanding the electric field assisted sintering of UO2 and non-stoichiometric oxides in general.

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Electric Field‐Induced Microstructural Evolution in Polycrystalline Bi₂O₃‐Doped ZnO in Presence of a Secondary Liquid Phase

Yan

Luo

2023

Adv Eng Mater

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Herein, a spectrum of electric field–induced microstructural evolution phenomena are observed in polycrystalline Bi2O3‐doped ZnO, and the underlying mechanisms are revealed. An applied electric field can drive the migration of bismuth (Bi) toward the negative electrode (including the motion of the charge‐neutral Bi‐rich liquid phase via electrochemical coupling), which produces a Bi‐free zone near the anode. The field‐induced migration of Bi creates a junction between electron‐conducting ZnO and ion‐conducting Bi2O3‐doped ZnO (via Bi2O3‐enriched liquid‐like intergranular films [IGFs]), where an oxygen ion current is converted to an electron current while generating O2 gas, generating a porosity belt. Aberration‐corrected electron microscopy further reveals the formation of three distinct types of grain boundaries (GBs). “Clean” ZnO GBs are observed near the anode, where Bi is depleted by the electric field. Bi2O3‐enriched liquid‐like IGFs (disordered GBs) are observed in the middle section. Near the cathode, electrochemical reduction induces an GB disorder–order transition to form fast‐moving Bi2O3‐enriched ordered GBs, which causes abnormal grain growth. Herein, several new field–matter interaction phenomena are discovered and an exemplar of field effects on microstructural evolution are established at multiple length scales in the presence of GB complexion (phase‐like) transitions.

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Grain growth in weak electric fields in strontium titanate: Grain growth acceleration by defect redistribution

Cited by 35 publications

References 52 publications

Grain growth in strontium titanate in electric fields: The impact of space‐charge on the grain‐boundary mobility

Grain growth in strontium titanate in electric fields: The impact of space‐charge on the grain‐boundary mobility

On the Role of the Electrical Field in Spark Plasma Sintering of UO2+x

Electric Field‐Induced Microstructural Evolution in Polycrystalline Bi₂O₃‐Doped ZnO in Presence of a Secondary Liquid Phase

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Grain growth in weak electric fields in strontium titanate: Grain growth acceleration by defect redistribution

Cited by 35 publications

References 52 publications

Grain growth in strontium titanate in electric fields: The impact of space‐charge on the grain‐boundary mobility

Grain growth in strontium titanate in electric fields: The impact of space‐charge on the grain‐boundary mobility

On the Role of the Electrical Field in Spark Plasma Sintering of UO2+x

Electric Field‐Induced Microstructural Evolution in Polycrystalline Bi2O3‐Doped ZnO in Presence of a Secondary Liquid Phase

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Product

Resources

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Electric Field‐Induced Microstructural Evolution in Polycrystalline Bi₂O₃‐Doped ZnO in Presence of a Secondary Liquid Phase