In-situ observation of oxygen mobility and abnormal lattice expansion in ceria during flash sintering

Jha, Shikhar Krishn; Charalambous, Harry; Wang, Han; Phuah, Xin Li; Mead, Christopher; Okasinski, John; Wang, Haiyan; Tsakalakos, Thomas

doi:10.1016/j.ceramint.2018.05.186

Cited by 79 publications

(44 citation statements)

References 80 publications

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“…Usually, the grain size becomes nonuniform, with evidence of redox reactions near the electrodes . The voltage expressed at the electrode is equal to the product of the current density and the interfacial resistance.…”

Section: Resultsmentioning

confidence: 99%

On the synchronicity of flash sintering and phase transformation

et al. 2019

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There is growing evidence that oxides of complex chemistries can be formed in one step by reactive flash sintering of their elemental constituents. Here we explore the temporal relationship between phase transformation and sintering by combining measurements of sintering with in situ measurements of phase transformation. The experiments are carried out under current rate, where flash is induced by injecting current and increasing it at a constant rate. We show that phase transformation of powders of magnesia and α‐alumina into single‐phase magnesium aluminate spinel was completed in 45 seconds, whereas sintering to full density required 60 seconds.

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Section: Resultsmentioning

confidence: 99%

On the synchronicity of flash sintering and phase transformation

et al. 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.…”

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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“…The flash method has been successfully applied to many different ceramics including ionic conductors like yttria‐stabilized zirconia and CeO 2 , electronic conductors, TiO 2 , ferroelectrics, BaTiO 3 , semiconductors and varistors, ZnO, perovskites, SrTiO 3 , and insulators, Al 2 O 3 and Y 2 O 3 . Typical characteristics of flash, the abrupt rise in conductivity and electroluminescence, are seen in dense polycrystals and single crystals as well …”

Section: Introductionmentioning

confidence: 99%

Processing and properties of Bi_0.98R_0.02FeO₃ (R = La, Sm, Y) ceramics flash sintered at ~650°C in <5 s

et al. 2019

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We show that flash sintering produces single‐phase, nanograin‐sized polycrystals of isovalent‐substituted multiferroic ceramics of complex compositions. Single‐phase polycrystals of Bi0.98R0.02FeO3 (R = La, Sm, Y) were produced at a furnace temperature of ~650°C in a few seconds by the application of an electric field of 50 V cm−1, with the current limit set to 40 mA mm−2. The dielectric and insulating properties compared favorably with expected values. Impedance spectroscopy suggests electrically homogenous microstructure, except for the sample Bi0.98La0.02FeO3 that shows a small grain boundary contribution to the impedance. These results reinforce the enabling nature of flash sintering for ceramics which pose difficulties in conventional sintering because they contain low melting constituents or develop secondary phases during the sintering protocol.

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In-situ observation of oxygen mobility and abnormal lattice expansion in ceria during flash sintering

Cited by 79 publications

References 80 publications

On the synchronicity of flash sintering and phase transformation

On the synchronicity of flash sintering and phase transformation

Field‐assisted heating of Gd‐doped ceria thin film

Processing and properties of Bi_0.98R_0.02FeO₃ (R = La, Sm, Y) ceramics flash sintered at ~650°C in <5 s

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In-situ observation of oxygen mobility and abnormal lattice expansion in ceria during flash sintering

Cited by 79 publications

References 80 publications

On the synchronicity of flash sintering and phase transformation

On the synchronicity of flash sintering and phase transformation

Field‐assisted heating of Gd‐doped ceria thin film

Processing and properties of Bi0.98R0.02FeO3 (R = La, Sm, Y) ceramics flash sintered at ~650°C in <5 s

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Product

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Processing and properties of Bi_0.98R_0.02FeO₃ (R = La, Sm, Y) ceramics flash sintered at ~650°C in <5 s