Rare Earth doped ceria: a combined X-ray and neutron pair distribution function study

2012 ◽  
Vol 227 (5) ◽  
pp. 272-279 ◽  
Author(s):  
Mauro Coduri ◽  
Michela Brunelli ◽  
Marco Scavini ◽  
Mattia Allieta ◽  
Paolo Masala ◽  
...  
Minerals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 272
Author(s):  
Seungyeol Lee ◽  
Huifang Xu ◽  
Hongwu Xu ◽  
Joerg Neuefeind

The crystal structure of moganite from the Mogán formation on Gran Canaria has been re-investigated using high-resolution synchrotron X-ray diffraction (XRD) and X-ray/neutron pair distribution function (PDF) analyses. Our study for the first time reports the anisotropic atomic displacement parameters (ADPs) of a natural moganite. Rietveld analysis of synchrotron XRD data determined the crystal structure of moganite with the space group I2/a. The refined unit-cell parameters are a = 8.7363(8), b = 4.8688(5), c = 10.7203(9) Å, and β = 90.212(4)°. The ADPs of Si and O in moganite were obtained from X-ray and neutron PDF analyses. The shapes and orientations of the anisotropic ellipsoids determined from X-ray and neutron measurements are similar. The anisotropic ellipsoids for O extend along planes perpendicular to the Si-Si axis of corner-sharing SiO4 tetrahedra, suggesting precession-like movement. Neutron PDF result confirms the occurrence of OH over some of the tetrahedral sites. We postulate that moganite nanomineral is stable with respect to quartz in hypersaline water. The ADPs of moganite show a similar trend as those of quartz determined by single-crystal XRD. In short, the combined methods can provide high-quality structural parameters of moganite nanomineral, including its ADPs and extra OH position at the surface. This approach can be used as an alternative means for solving the structures of crystals that are not large enough for single-crystal XRD measurements, such as fine-grained and nanocrystalline minerals formed in various geological environments.


Coatings ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 724
Author(s):  
Sara Massardo ◽  
Alessandro Cingolani ◽  
Cristina Artini

Rare earth-doped ceria thin films are currently thoroughly studied to be used in miniaturized solid oxide cells, memristive devices and gas sensors. The employment in such different application fields derives from the most remarkable property of this material, namely ionic conductivity, occurring through the mobility of oxygen ions above a certain threshold temperature. This feature is in turn limited by the association of defects, which hinders the movement of ions through the lattice. In addition to these issues, ionic conductivity in thin films is dominated by the presence of the film/substrate interface, where a strain can arise as a consequence of lattice mismatch. A tensile strain, in particular, when not released through the occurrence of dislocations, enhances ionic conduction through the reduction of activation energy. Within this complex framework, high pressure X-ray diffraction investigations performed on the bulk material are of great help in estimating the bulk modulus of the material, and hence its compressibility, namely its tolerance toward the application of a compressive/tensile stress. In this review, an overview is given about the correlation between structure and transport properties in rare earth-doped ceria films, and the role of high pressure X-ray diffraction studies in the selection of the most proper compositions for the design of thin films.


2013 ◽  
Vol 15 (22) ◽  
pp. 8495 ◽  
Author(s):  
Mauro Coduri ◽  
Marco Scavini ◽  
Michela Brunelli ◽  
Paolo Masala

2019 ◽  
Vol 31 (14) ◽  
pp. 5024-5034 ◽  
Author(s):  
Wojciech A. Sławiński ◽  
Helen Y. Playford ◽  
Stephen Hull ◽  
Stefan T. Norberg ◽  
Sten G. Eriksson ◽  
...  

Inorganics ◽  
2019 ◽  
Vol 7 (8) ◽  
pp. 102
Author(s):  
Mauro Coduri ◽  
Dario Bozzetti ◽  
Stefano Checchia ◽  
Michela Brunelli ◽  
Marco Scavini

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.


2011 ◽  
Vol 45 (23) ◽  
pp. 9883-9890 ◽  
Author(s):  
Richard Harrington ◽  
Douglas B. Hausner ◽  
Wenqian Xu ◽  
Narayan Bhandari ◽  
F. Marc Michel ◽  
...  

2011 ◽  
Vol 18 (2) ◽  
pp. 266-271 ◽  
Author(s):  
Hester Esna du Plessis ◽  
J. P. R. de Villiers ◽  
G. J. Kruger ◽  
A. Steuwer ◽  
M. Brunelli

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