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Vandemeulebroucke, D.; Batuk, M.; Hajizadeh, A.; Wastiaux, M.; Roussel, P.; Hadermann, J. |
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Title |
Incommensurate Modulations and Perovskite Growth in LaxSr2–xMnO4−δAffecting Solid Oxide Fuel Cell Conductivity |
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A1 Journal Article |
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Year  |
2024 |
Publication |
Chemistry of Materials |
Abbreviated Journal |
Chem. Mater. |
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Keywords |
A1 Journal Article; Electron Microscopy for Materials Science (EMAT) ; |
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Abstract |
Ruddlesden-Popper La????Sr2−????MnO4−???? materials are interesting symmetric solid oxide
fuel cell electrodes due to their good redox stability, mixed ionic and electronic conducting behavior and thermal expansion that matches well with common electrolytes. In reducing environments – as at a solid oxide fuel cell anode – the x = 0.5 member, i.e. La0.5Sr1.5MnO4−????, has a much higher total conductivity than compounds with a different La/Sr ratio, although all those compositions have the same K2NiF4-type I4/mmm structure. The origin for this conductivity difference is not yet known in literature. Now, a combination of in-situ and ex-situ 3D electron diffraction, high-resolution imaging, energy-dispersive X-ray analysis and electron energy-loss spectroscopy uncovered clear differences between x=0.25 and x=0.5 in the pristine structure, as well as in the transformations upon high-temperature reduction. In La0.5Sr1.5MnO4−????, Ruddlesden-Popper n=2 layer defects and an amorphous surface layer are present, but not in La0.25Sr1.75MnO4−????. After annealing at 700°C in 5% H2/Ar, La0.25Sr1.75MnO4−???? transforms to a tetragonal 2D incommensurately modulated structure with modulation vectors ⃗????1 = 0.2848(1) · (⃗????* +⃗????*) and ⃗????2 =0.2848(1) · (⃗????* – ⃗????*), whereas La0.5Sr1.5MnO4−???? only partially transforms to an orthorhombic 1D incommensurately modulated structure,
with ⃗???? = 0.318(2) · ⃗????*. Perovskite domains grow at the crystal edge at 700°C in 5%
H2 or vacuum, due to the higher La concentration on the surface compared to the bulk, which leads to a different thermodynamic equilibrium. Since it is known that a lower degree of oxygen vacancy ordering and a higher amount of perovskite blocks enhance oxygen mobility, those differences in defect structure and structural transformation upon reduction, might all contribute to the higher conductivity of La0.5Sr1.5MnO4−???? in solid oxide fuel cell anode conditions compared to other La/Sr ratios. |
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English |
Wos |
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Publication Date |
2024-02-20 |
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ISSN |
0897-4756 |
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Impact Factor |
8.6 |
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Notes |
Universiteit Antwerpen, BOF TOP 38689 ; Fonds Wetenschappelijk Onderzoek, I003218N ; European Commission NanED, 956099 ; |
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Most recent IF: 8.6; 2024 IF: 9.466 |
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Call Number |
EMAT @ emat @ |
Serial |
8997 |
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Author |
Sa, J.; Hu, N.; Heyvaert, W.; Van Gordon, K.; Li, H.; Wang, L.; Bals, S.; Liz-Marzán, L.M.; Ni, W. |
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Title |
Spontaneous Chirality Evolved at the Au–Ag Interface in Plasmonic Nanorods |
Type |
A1 Journal Article |
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Year |
2023 |
Publication |
Chemistry of materials |
Abbreviated Journal |
Chem. Mater. |
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Keywords |
A1 Journal article; Electron microscopy for materials research (EMAT) |
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Abstract |
Chiral ligands are considered a required ingredient during the synthesis of dissymmetric plasmonic metal nanocrystals. The mechanism behind the generation of chiral structures involves the formation of high Miller index chiral facets, induced by the adsorption of such chiral ligands. We found however that, chirality can also evolve spontaneously, without the involvement of any chiral ligands, during the co-deposition of Au and Ag on Au nanorods. When using a specific Au/Ag ratio, phase segregation of the two metals leads to an interface within the obtained AuAg shell, which can be exposed by removing the Ag component via oxidative etching. Although a close-to-racemic mixture of chiral Au nanorods with right and left handedness is found in solution, electron tomography analysis evidences left- and righthanded helicities, both at the Au-Ag interface and at the exposed surface of Au NRs after Ag etching. The helicity profile of the NRs indicates dominating inclination angles in a range from 30° to 60°. Single-particle optical characterization also reveals random handedness in the plasmonic response of individual nanorods. We hypothesize that, the origin of chirality is related with symmetry breaking during the co-deposition of Au and Ag, through an initial perturbation in a small region on the Au-Ag interface that eventually leads to chiral segregation throughout the nanocrystal. |
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001052093300001 |
Publication Date |
2023-08-21 |
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ISSN |
0897-4756 |
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Additional Links |
UA library record; WoS full record |
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Impact Factor |
8.6 |
Times cited |
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Open Access |
Not_Open_Access: Available from 22.02.2024 |
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Notes |
The authors acknowledge the financial support from the National Natural Science Foundation of China (grant 22074102). LMLM acknowledges funding from 26 MCIN/AEI/10.13039/501100011033 and “ESF Investing in your future” (Grant PID2020- 117779RB-I00). This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 823717 – ESTEEM3.; Ministerio de Ciencia e Innovaci?n, PID2020-117779RB-I00 ; H2020 Research Infrastructures, 823717 ; European Social Fund, PID2020-117779RB-I00 ; National Natural Science Foundation of China, 22074102 ; |
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Most recent IF: 8.6; 2023 IF: 9.466 |
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Call Number |
EMAT @ emat @c:irua:198151 |
Serial |
8810 |
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