Strontium surface segregation in La0.6Sr0.4Co0.2Fe0.8O3−δ subjected to mechanical stress

Araki, Wakako; Miyashita, M.; Arai, Yasuhiko

doi:10.1016/j.ssi.2016.04.003

Cited by 29 publications

(11 citation statements)

References 18 publications

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“…For materials such as LSCF the mechanical properties and their effect upon A-site segregation have been studied in much less detail. It has been shown that external stresses can affect the growth rate of strontium-based secondary phases 14 , however, the precise cause for this alteration is not yet known. LSCF exhibits a domain like structure [15][16][17] as a result of shared Laue group symmetries found in the R3c space group, however, the effect this twinned microstructure has upon strontium segregation is also unknown.…”

Section: Introductionmentioning

confidence: 99%

In situ study of strontium segregation in La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ in ambient atmospheres using high-temperature environmental scanning electron microscopy

et al. 2018

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Section: Introductionmentioning

confidence: 99%

In situ study of strontium segregation in La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ in ambient atmospheres using high-temperature environmental scanning electron microscopy

et al. 2018

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“…More details on the sample preparation can be found in the literature. 2,26 In the indentation test, a relatively large sapphire indenter with radius 500 m (made of a sapphire ball lens) was used, whilst a diamond indenter with radius 25 m was also used for comparison. (It should be noted that the effective tip radius of the diamond indenter was actually determined to be 15 m based on a preliminary test with a reference sample of quartz.)…”

Section: Spherical Indentationmentioning

confidence: 99%

Can ferrroelasticity be evaluated by nanoindentation?

Araki

Wang

Atkinson

2018

Journal of the European Ceramic Society

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The present study investigated the possibility of evaluating ferroelastic mechanical characteristics by spherical indentation. Finite element simulation of spherical indentation with a relatively large sphere of a ferroelastic-plastic material was performed using characteristic bulk data of a typical ferroelastic oxide (La-Sr-Co-Fe-O). The simulation results showed that the ferroelastic mechanical behaviour cannot be observed in the indentation load vs depth curve, but is clearly observable in the indentation stress vs indentation strain curve, which can be obtained reliably in experiments by estimating the contact radius using load-partial unloading sequences. The method can be reliable when the indentation stress is under the upper ferroelastic critical stress. Therefore, in principle ferroelastic mechanical characteristics could be evaluated by spherical indentation by obtaining the indentation stress vs indentation strain curve using partial unloading to estimate the contact radius, although the requirements are very difficult to satisfy in actual experiments.

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“…[6][7][8] However, various studies have shown that Sr tends to segregate to the surface via the grain boundaries to relieve mechanical stress in the material which occurs due to the mismatch in the ionic radii of La 3+ (XII) (1.36 Å) and Sr 2+ (XII) (1.44 Å). [9][10][11][12][13][14] Lee et al 15 performed an experimental study on the segregation of Ba 2+ , Ca 2+ , and Sr 2+ in LnMnO 3 (Ln = La, Sm) which was complemented by density functional theory (DFT) calculations and analytical modelling. The results showed that the segregation of the alkaline earth metal ions is driven not only by elastic energy minimization (due to the size mismatch of La 3+ and Ba 2+ /Sr 2+ /Ca 2+ ) but also by electrostatic forces.…”

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confidence: 99%

Impact of SO₂on the Oxygen Exchange Kinetics of the Promising SOFC/SOEC Air Electrode Material La_0.8Ca_0.2FeO_3-δ

Berger

Bucher

Gspan

et al. 2017

J. Electrochem. Soc.

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The mass and charge transport properties of La 0.8 Ca 0.2 FeO 3-δ (LCF82) were determined at 600-800 • C and pO 2 = 0.1 bar. The electronic conductivity is in the range of 112 S cm −1 at 700 • C. The chemical surface exchange coefficient (k chem ) and the chemical diffusion coefficient of oxygen (D chem ) were measured. LCF82 shows exceptionally fast oxygen exchange kinetics in pure O 2 -Ar at 700 • C. Long-term measurements at 700 • C in pure O 2 -Ar showed an excellent stability of the kinetic parameters during 1000 h. However, when 2 ppm of sulfur dioxide were added, k chem decreased by a factor of 40 within the first 24 h. After further 1000 h, the total decrease in k chem amounted to two orders of magnitude. Post-test analyses of LCF82 were performed by SEM-EDXS, XPS, and STEM. Ca-enrichment and La-/Fe-depletion of the LCF82 surface occurred during the first 1000 h without SO 2 . At the surface of the sample exposed to 2 ppm SO 2 for additional 1000 h, CaSO 4 crystals with diameters of 1-2 μm and an underlying layer of Fe 2 O 3 (thickness approx. 300-450 nm) were found. Remarkably, LCF82 shows faster oxygen exchange kinetics than La 0.6 Sr 0.4 CoO 3-δ even in the degraded state. Therefore, LCF82 is suggested as a promising material for SOFC and SOEC air electrodes.

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Strontium surface segregation in La0.6Sr0.4Co0.2Fe0.8O3−δ subjected to mechanical stress

Cited by 29 publications

References 18 publications

In situ study of strontium segregation in La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ in ambient atmospheres using high-temperature environmental scanning electron microscopy

In situ study of strontium segregation in La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ in ambient atmospheres using high-temperature environmental scanning electron microscopy

Can ferrroelasticity be evaluated by nanoindentation?

Impact of SO₂on the Oxygen Exchange Kinetics of the Promising SOFC/SOEC Air Electrode Material La_0.8Ca_0.2FeO_3-δ

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Strontium surface segregation in La0.6Sr0.4Co0.2Fe0.8O3−δ subjected to mechanical stress

Cited by 29 publications

References 18 publications

In situ study of strontium segregation in La0.6Sr0.4Co0.2Fe0.8O3−δ in ambient atmospheres using high-temperature environmental scanning electron microscopy

In situ study of strontium segregation in La0.6Sr0.4Co0.2Fe0.8O3−δ in ambient atmospheres using high-temperature environmental scanning electron microscopy

Can ferrroelasticity be evaluated by nanoindentation?

Impact of SO2on the Oxygen Exchange Kinetics of the Promising SOFC/SOEC Air Electrode Material La0.8Ca0.2FeO3-δ

Contact Info

Product

Resources

About

In situ study of strontium segregation in La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ in ambient atmospheres using high-temperature environmental scanning electron microscopy

In situ study of strontium segregation in La_0.6Sr_0.4Co_0.2Fe_0.8O_3−δ in ambient atmospheres using high-temperature environmental scanning electron microscopy

Impact of SO₂on the Oxygen Exchange Kinetics of the Promising SOFC/SOEC Air Electrode Material La_0.8Ca_0.2FeO_3-δ