The role of point defects and defect gradients in flash sintering of perovskite oxides

Rheinheimer, Wolfgang; Phuah, Xin Li; Wang, Han; Lemke, Fabian; Hoffmann, Michael J.; Wang, Haiyan

doi:10.1016/j.actamat.2018.12.007

Cited by 81 publications

(56 citation statements)

References 64 publications

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“…1,11,17 Mechanisms that have been proposed to explain flash sintering include: I. Direct thermal and electric field-induced nucleation of a large number of point defects, 16,[18][19][20][21] II. Nucleation of a non-equilibrium phase, which in turn results in a high number of point defects that enhance mass transport, 15,22 III.…”

Section: Introductionmentioning

confidence: 99%

Selective laser flash sintering of 8‐YSZ

2019

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Flash sintering of ceramics is characterized by rapid sintering during simultaneous application of electric field and heat. Previous studies of flash sintering have been conducted in furnace environments, where sample temperatures are approximately uniform. In this work, we use highly dynamic heating from a scanning laser to initiate flash sintering while simultaneously applying a DC electric field. Onset of flash sintering is determined by a measurable increase in current through the sample. Our results show that stage I and stage II flash sintering can be initiated by laser heating. At low‐to‐moderate combinations of laser energies and applied electric fields, measured current rises slightly when the laser is scanned completely across the specimen from the positive to the negative electrodes. Microstructures for these samples show that powder consolidation is minimal in this regime (stage I flash sintering), and thus the observed current is likely due to onset of neck growth between powder particles rather than densification. At higher laser energies and fields, current rises steeply and microstructures show significant consolidation (stage II flash sintering). The demonstration that flash sintering occurs when ceramic is heated by laser‐scanning supports future utilization of selective laser flash sintering as an additive manufacturing process.

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Section: Introductionmentioning

confidence: 99%

Selective laser flash sintering of 8‐YSZ

2019

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“…It is likely that the middle section had larger cluster size since that section experienced less heat loss to the surroundings compared to the electrode ends, resulting in increased coarsening. On the contrary, the asymmetric distribution is likely related to the electric field, as it has shown to affect the grain growth behavior between the anode and cathode electrodes …”

Section: Resultsmentioning

confidence: 99%

“…On the contrary, the asymmetric distribution is likely related to the electric field, as it has shown to affect the grain growth behavior between the anode and cathode electrodes. 6,12,[14][15][16]26 Figure 4A shows the temperature dependence of the conductivity of the three thin film specimens based on in-plane measurements. The activation energies were estimated based on the linear fitting of the Arrhenius plots.…”

Section: Resultsmentioning

confidence: 99%

“…For example, in situ synchrotron studies 9 have observed metastable phase transformations 10,11 and abnormal lattice expansions across the sample 12,13 during flash sintering. Microstructure characterization after flash sintering revealed asymmetric grain growth, [14][15][16] texturing, 3,17 and high density of defects, 3,17,18 as a result of the generation and mobility of the charged species caused by the applied DC field. In conventional sintering, bulk ceramics typically do not have any these unique characteristics.…”

Section: Introductionmentioning

confidence: 99%

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Field‐assisted heating of Gd‐doped ceria thin film

Phuah

Misra

et al. 2019

J Am Ceram Soc

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Flash sintering has recently been used to sinter various bulk ceramics under reduced sintering temperatures and sintering time by applying an electric field across the sample. In this work, we have demonstrated field-assisted heating of 10 mol% Gddoped CeO 2 thin films deposited by pulsed laser deposition. Microstructure analysis revealed the elongated grains aligned in the out-of-plane direction which is perpendicular to the direction of electric field. The overall microstructure of the flashheated thin film also contained a matrix of porous and clustered regions, which are distributed throughout the thin film from the anode to cathode electrode regions. The flash-heated thin film showed significantly different conductivity and optical permittivity compared to the as-grown thin films. This demonstration suggests a feasible approach for post-deposition synthesis of thin films using field-assisted heating toward novel morphologies and properties. K E Y W O R D Sconductivity, flash sintering, microstructure, permittivity, thin films

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“…There are several features of porous MIEC materials that have an impact on the performance of the electrode. The microstructure of the electrode (porosity, tortuosity, particle size) [2,3], intrinsic oxygen activity (surface exchange, oxygen diffusion) [4,5], interface between the electrode and electrolyte or the barrier layer [6], and the electronic transport properties are all very important. The most studied group of MIEC oxygen electrode materials are the perovskites [7][8][9].…”

Section: Introductionmentioning

confidence: 99%

Effect of sintering temperature on electrochemical performance of porous SrTi1-xFexO3-δ (x = 0.35, 0.5, 0.7) oxygen electrodes for solid oxide cells

Mroziński

Molin

Jasiński

2020

J Solid State Electrochem

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This work evaluates the effects of the sintering temperature (800°C, 900°C, 1000°C) of SrTi 1-x Fe x O 3-δ (x = 0.35, 0.5, 0.7) porous electrodes on their electrochemical performance as potential oxygen electrode materials of solid oxide cells. The materials were prepared by a solid-state reaction method and revealed the expected cubic perovskite structure. After milling, the powders were characterised by a sub-micrometre particle size with high sinter-activity. It was shown that the lowest area specific resistance was achieved after sintering SrTi 0.65 Fe 0.35 O 3 electrodes at 1000°C, and SrTi 0.5 Fe 0.5 O 3 and SrTi 0.30 Fe 0.70 O 3 electrodes at 800°C, which can be considered to be a relatively low temperature. In general, EIS measurements showed that increasing the Fe content results in lowered electrode polarisation and a decrease of the series resistance. Even though the studied materials have much lower total conductivities than state-of-the-art electrode materials (e.g. (La,Sr)(Co,Fe)O 3 ), the polarisation resistances obtained in this work can be considered low.

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The role of point defects and defect gradients in flash sintering of perovskite oxides

Cited by 81 publications

References 64 publications

Selective laser flash sintering of 8‐YSZ

Selective laser flash sintering of 8‐YSZ

Field‐assisted heating of Gd‐doped ceria thin film

Effect of sintering temperature on electrochemical performance of porous SrTi1-xFexO3-δ (x = 0.35, 0.5, 0.7) oxygen electrodes for solid oxide cells

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