| 1. |
- Coduri, Mauro, et al.
(författare)
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Local and average structure of Yb-doped ceria through synchrotron and neutron pair distribution function
- 2019
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Ingår i: Inorganics. - : MDPI AG. - 2304-6740. ; 7:8
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Tidskriftsartikel (refereegranskat)abstract
- As transport properties of doped ceria electrolytes depend significantly on the nature of the dopant and the defectivity, the design of new materials and devices requires proper understanding of the defect structure. Among lanthanide dopants, Yb shows some peculiar characteristics that call for a possible different defect structure compared to Gd and Sm conventional dopants, which could be linked to its poorer performance. For this purpose, we combine synchrotron and neutron powder diffraction exploiting the Rietveld and Pair distribution Function. By increasing its concentration, Yb produces qualitatively the same structural distortions as other dopants, leading to a domain structure involving the progressive nucleation and growth of nanodomains with a Yb2O3-like (C-type) structure hosted in a fluorite CeO2 matrix. However, when it comes to growing the C-type nanodomains into a long-range phase, the transformation is less pronounced. At the same time, a stronger structural distortion occurs at the local scale, which is consistent with the segregation of a large amount of oxygen vacancies. The strong trapping of VOs by Yb3+ explains the poor performance of Yb-doped ceria with respect to conventional Sm-, Gd-, and Y-doped samples at equal temperature and dopant amount.
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| 2. |
- Coduri, Mauro, et al.
(författare)
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Local structure and magnetism of Fe2O3 maghemite nanocrystals : The role of crystal dimension
- 2020
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Ingår i: Nanomaterials. - : MDPI AG. - 2079-4991. ; 10:5
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Tidskriftsartikel (refereegranskat)abstract
- Here we report on the impact of reducing the crystalline size on the structural and magnetic properties of γ-Fe2O3 maghemite nanoparticles. A set of polycrystalline specimens with crystallite size ranging from ~2 to ~50 nm was obtained combining microwave plasma synthesis and commercial samples. Crystallite size was derived by electron microscopy and synchrotron powder diffraction, which was used also to investigate the crystallographic structure. The local atomic structure was inquired combining pair distribution function (PDF) and X-ray absorption spectroscopy (XAS). PDF revealed that reducing the crystal dimension induces the depletion of the amount of Fe tetrahedral sites. XAS confirmed significant bond distance expansion and a loose Fe-Fe connectivity between octahedral and tetrahedral sites. Molecular dynamics revealed important surface effects, whose implementation in PDF reproduces the first shells of experimental curves. The structural disorder affects the magnetic properties more and more with decreasing the nanoparticle size. In particular, the saturation magnetization reduces, revealing a spin canting effect. Moreover, a large effective magnetic anisotropy is measured at low temperature together with an exchange bias effect, a behavior that we related to the existence of a highly disordered glassy magnetic phase.
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| 3. |
- Coduri, Mauro, et al.
(författare)
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Structure-property correlation in oxide-ion and proton conductors for clean energy applications: recent experimental and computational advancements
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7496 .- 2050-7488. ; 10, s. 5082-5110
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Forskningsöversikt (refereegranskat)abstract
- In the last decade, the field of oxide-ion and proton conductors continued to trigger a significant amount of basic research aimed at improving the properties and the comprehension of actual materials, as well as at discovering novel phases. This need comes from the current and future urgent requests of changing our energy management towards cleaner solutions such as solid oxide fuel cells. In this review article, we highlight the most recent advancements in this exciting field by putting particular emphasis on the structure-property correlations in oxide-ion and proton conductors both from an experimental and a computational perspective. Special focus is laid on developments in the area of operando and in situ spectroscopy, machine learning and high-throughput approaches to accelerate the discovery of new and advanced materials.
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| 4. |
- Morana, Marta, et al.
(författare)
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Cubic or Not Cubic? Combined Experimental and Computational Investigation of the Short-Range Order of Tin Halide Perovskites
- 2023
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Ingår i: Journal of Physical Chemistry Letters. - : American Chemical Society (ACS). - 1948-7185. ; 14, s. 2178-2186
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Tidskriftsartikel (refereegranskat)abstract
- Tin-based metal halide perovskites with a composition of ASnX3 (where A= MA or FA and X = I or Br) have been investigated by means of X-ray total scattering techniques coupled to pair distribution function (PDF) analysis. These studies revealed that that none of the four perovskites has a cubic symmetry at the local scale and that a degree of increasing distortion is always present, in particular when the cation size is increased, i.e., from MA to FA, and the hardness of the anion is increased, i.e., from Br- to I-. Electronic structure calculations provided good agreement with experimental band gaps for the four perovskites when local dynamical distortions were included in the calculations. The averaged structure obtained from molecular dynamics simulations was consistent with experimental local structures determined via X-ray PDF, thus highlighting the robustness of computational modeling and strengthening the correlation between experimental and computational results.
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