Percolating hierarchical defect structures drive phase transformation in Ce1−xGdxO2−x/2: a total scattering study

Scavini, Marco; Coduri, Mauro; Allieta, Mattia; Masala, Paolo; Cappelli, S.; Oliva, Cesare; Brunelli, Michela; Orsini, F.; Ferrero, C.

doi:10.1107/s2052252515011641

Cited by 28 publications

(43 citation statements)

References 48 publications

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“…The two-phase model significantly improves the fit, especially in the region featuring M-M distances. Similar results were already observed in ceria doped with Y [23,35], Sm [25], Gd [24,39], Bi [40], Zr [41], Pr, Tb [16], and La [42]. This is also consistent with recent absorption spectroscopy study, where a bimodal distribution of bond lengths was observed in Y-and Sm-doped ceria compounds [43].…”

Section: Local Structure-x-raysupporting

confidence: 91%

“…The (413) reflection is already observed for Yb375, even though with small intensity and large broadening, about four times broader than structure peaks. This phenomenon, consistent with the existence of anti-phase boundaries due to the nucleation and growth of C-type nanodomains starting on different sites, is consistent with the hierarchical structures already observed for Y, Gd, and Sm and described as C* [23][24][25]. Lastly, x(M2) is very close to 0 (−0.003), indicating that only a slight C-type distortion occurs.…”

Section: Long-range Structuresupporting

confidence: 89%

“…For Yb500, however, x(M2) does not vary significantly and the structure can be defined as fully C-type. Domain size in Yb250 is smaller than in samples of ceria doped with the same concentration of Y, Sm, and Gd, which feature 10-12 nm domains estimated with the same method [23][24][25].…”

Section: Local Structure-x-raymentioning

confidence: 88%

“…Structural evolution linked with heavy doping is an important factor to understand and to estimate the way defects interact at lower dopant concentration. Indeed, it was proved recently by PDF that for Y [23], Gd [22,24], and Sm [25], the fluorite to C-type transformation occurs via nucleation and growth of distorted C-type nanodomains that merge and percolate at a critical dopant concentration. This makes heavily doped ceria structure a hybrid between those of fluorite and C-type [5,26].…”

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confidence: 99%

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Local and Average Structure of Yb-Doped Ceria through Synchrotron and Neutron Pair Distribution Function

et al. 2019

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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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Section: Local Structure-x-raysupporting

confidence: 91%

Section: Long-range Structuresupporting

confidence: 89%

Section: Local Structure-x-raymentioning

confidence: 88%

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confidence: 99%

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Local and Average Structure of Yb-Doped Ceria through Synchrotron and Neutron Pair Distribution Function

et al. 2019

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“…Jensen et al (2015) explore the use of PDF approaches in the study of thin films and show how the information obtained on local structure helps open up the field of local structural analyses of thin films and gives insight into crystallization processes. While Scavini et al (2015) combine PDF analyses with ESR to reveal fascinating new information on the widely studied solid electrolyte Gd/CeO 2 and obtain unique information on both local and intermediate range structure in this disordered material by showing how small defect clusters condense into nanodomains. The role of PDF in exploring meso-scale structure is further discussed and illustrated in the article of Egami (2015).…”

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confidence: 99%

Challenges in the structural science of materials

Catlow

2016

Int Union Crystallogr J

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The articles published recently in IUCrJ continue to exemplify the developments and challenges in the structural science of materials. They illustrate the exciting rapid developments in technique, sources, instrumentation and data analysis, the continuing role and growing power of computation in the field, and the increasing ability to investigate complex structural problems in materials that are of direct relevance to their function.Advances in technique and data analysis are well illustrated by the review article of Van Aert et al. (2016) which describes how developments in transmission electron microscopy coupled with novel data analysis methods can give accurate structural information on nanostructured and disordered materials; and illustrates how increased precision can be achieved in atomic positions using these techniques. Several examples illustrate the power of the approach, for example the accurate information on atomic coordinates adjacent to a twin boundary in CaTiO 3 , as illustrated in Fig. 1.Significant developments in techniques are also described in the article of Rius et al. (2015), who describe how the synchrotron-based through-the-substrate X-ray microdiffraction technique (tts-XRD) can now be used to obtain structural information on microvolumes of crystals embedded in a complex matrix -a development of importance for several areas of materials science including the study of complex mineralogical samples. The use of synchrotron radiation in operando methods in structural science, particularly relating to catalytic systems, continues to grow as illustrated by the recent study of Lezcano-Gonzá lez et al. (2016) who investigated complex structural changes during the operation of a microporous dehydroaromatization catalyst.A core area of crystallography is of course the determination and modelling of electron density, recent developments in which are discussed in the article of Macchi et al. (2015), who emphasize multi-technique approaches, and show the importance of developments in sources and detectors and of new multipole models for describing charge densities accurately. Related topics are considered in the article of Sanjuan-Szklarz et al. (2016), which discusses how improved accuracy may be obtained by using transferable aspherical atom models (TAAM) in structure refinements and how such an approach can yield highquality structures even from low-resolution data.

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Phase Stability of High Entropy (Mg,Ni,Co,Cu,Zn)O from Temperature‐Resolved Synchrotron Diffraction: Tetragonal Distortion and Guggenite Phase

Coduri,

Fracchia,

Checchia

et al. 2024

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The temperature‐resolved structure evolution of quinary and quaternary equimolar oxides containing Mg, Ni, Zn, Co, and Cu is investigated by in situ synchrotron diffraction. Important structural modifications occur already at mild temperatures and depend on the elements involved. All quaternary compounds with χ(Cu) = 0.25 within 250–500 °C show a tetragonal phase. The fraction of Cu dictates the degree of the tetragonal distortion: for χ(Cu) = 0.20 only local distortions are observed, which do not occur in the absence of Cu. Further heating restores the original cubic phase, followed by the segregation of other phases, which depend on the elements available. In the presence of both Cu and Mg, the segregation of guggenite is observed, a phase with a cation connectivity similar to the cubic high entropy oxide, but with a suitable coordination environment for Cu atoms by allowing strong elongation of octahedra. Guggenite acts as a buffer layer facilitating the gradual diffusion of Cu2+ from the cubic high entropy oxide to tenorite. To conclude, it is demonstrated for the first time that the demixing of the prototypal high entropy oxide does not involve just tenorite or binary oxides, it is rather mediated by the formation of guggenite.

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Percolating hierarchical defect structures drive phase transformation in Ce_1−xGd_xO_2−x/2: a total scattering study

Cited by 28 publications

References 48 publications

Local and Average Structure of Yb-Doped Ceria through Synchrotron and Neutron Pair Distribution Function

Local and Average Structure of Yb-Doped Ceria through Synchrotron and Neutron Pair Distribution Function

Challenges in the structural science of materials

Phase Stability of High Entropy (Mg,Ni,Co,Cu,Zn)O from Temperature‐Resolved Synchrotron Diffraction: Tetragonal Distortion and Guggenite Phase

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