In situ pair distribution function study on lanthanum doped ceria

Abstract

Doped ceria materials are widely studied for their application in solid oxide fuel cell devices. In this work we report on the average and local structure evolution of La-doped ceria (Ce(1-x)La(x)O(2-x/2), x = 0.25) under fuel cells' operating conditions. The effect of doping on the average structure is investigated using conventional Rietveld analysis of neutron powder diffraction data. The extent of disorder as well as the local structure evolution at high temperature are investigated by employing very hard X-rays under both air and reducing atmosphere.

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

“…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].…”

Structural characterization of Tb- and Pr-doped ceria

“…It is instead not observed in Pr-doped samples for x ≤ 0.500. Previous PDF investigations [3,8,18,[32][33][34] demonstrated that this peak is the fingerprint of a longer M-M pair, arising from the ordering of oxygen vacancies and trivalent cations, reminiscent of a lower symmetry phase occurring, at least, at the local scale. It is also evident that the larger the Tb-doping amount, the larger the area of the peak: the area of the long M-M pair peak normalized to the one of the fluorite M-M distance (~3.8 Å) is plotted in Fig.…”

Size and spatial correlation of defective domains in yttrium-doped CeO2

“…The PDF technique is also bulk-probing, as it relies on the scattered intensity from all the active volume of the sample. These capabilities are well suited to studying doped ceria, which brings in the so-called nanostructure problem (Billinge and Levin, 2007): the structure of concern is singlephase though perturbed on average by large, doping-induced static disorder, as inferred from the compositional evolution of atomic displacement parameters (Coduri et al, 2012a(Coduri et al, , 2012b(Coduri et al, , 2013bScavini et al, 2012).…”

“…sub-nanometre regions with a distorted fluorite (CeO 2 ) or C-type (dopant oxide) structure. The relative amount of the two kinds of droplets follows the compound stoichiometry (Coduri et al, 2012a(Coduri et al, , 2012b(Coduri et al, , 2013bScavini et al, 2012).…”

“…APDBs, appearing in the Q-space patterns as the selective line broadening of superstructure reflections (Coduri et al, 2013b), gradually fade with increasing dopant concentration.…”