Defect thermodynamic and transport properties of nanocrystalline Gd-doped ceria

Abstract

Nanocrystalline CeO 2 -doped (5, 7.5, 10, and 15 mol%) Gd 2 O 3 powders, with a particle size of about 17 nm, were synthesized through the combustion of glycine/ nitrate gels. Dense nanocrystalline materials were obtained by hot uniaxial sintering. Optical microscopy, scanning electron microscopy and transmission electron microscopy examinations, as well as X-ray diffraction analyses, have allowed us to characterize these polycrystals. The grain sizes, included between ∼10 and 80 nm, depend on both the sintering temperature and the amount of dopant. A comparison of the transport properties of these nanocrystalline samples to the values obtained with coarsened grained materials of same composition shows that the ionic conductivity passes through a maximum for mean grain sizes included between 300 and 500 nm. Furthermore, an enhancement of the ionic conductivity is observed when the amount of dopant increases. This was attributed to a grain-size-dependent gadolinium segregation at the periphery of the grains confirmed by X-ray photoelectron spectroscopy characterizations.

Ionic and Electronic Conductivity of Nanostructured, Samaria-Doped Ceria

“…As indicated in Table I, the early work of Chiang 8 agrees with the expectation that, in contrast to undoped ceria, nanostructuring in the presence of trivalent dopants decreases overall conductivity; even for grain sizes of only 10 nm, distinct bulk and grain boundary responses were detected in the impedance spectra with grain boundaries adding to the overall material resistance. The result is supported by more recent work from Jasinski, 13 Surble et al, 14 Perez-Coll et al, 15 and Ruiz-Trejo et al 16 While the later studies have been directed toward the exploration of H 2 O uptake and proton transport along grain boundaries, the data nevertheless reveal that doped ceria with grain size of ∼100 nm has resistive grain boundaries. The works of Bellino et al 17 and of Anselmi-Tamburini et al 18 stand in stark contrast to these studies.…”

“…The result is supported by more recent work from Jasinski, 13 Surble et al, 14 PerezColl et al, 15 and Ruiz-Trejo et al 16 While the later studies have been directed toward the exploration of H 2 O uptake and proton transport along grain boundaries, the data nevertheless reveal that doped ceria with grain size of ∼100 nm has resistive grain boundaries. The works of Bellino et al 17 and of Anselmi-Tamburini et al 18 stand in stark contrast to these studies.…”

Facile Conversion of Layered Ruddlesden−Popper-Related Structure Y2O3-Doped Sr2CeO4 into Fast Oxide Ion-Conducting Fluorite-Type Y2O3-Doped CeO2

“…22 There are several synthesis methods, including conventional ceramic (solid-state) and soft-chemical methods such as glycine-nitrate, 27 coprecipitation, 28 and polymerization, 29 that are employed to prepare doped ceria electrolytes. These preparation methods play a significant role in determining the microstructure and particle size distributions, which influence the electrical conductivity, [30][31][32][33] and particlesize-dependent conductivity was explained using the space charge model. 34,35 Recently, we have re-examined the chemical stability of Y-doped BaCeO 3 in CO 2 at a temperature range of 600-1000 °C.…”

Studies on chemical stability in CO2 and H2O and electrical conductivity of perovskite-type Ba3In2Zr1−x Ce x O8 (x = 0, 0.5, 1)

“…Nonetheless, it is also important to mention here that the electrical conductivity of materials significantly changes with crystalline sizes. For example, Surble et al [52] showed that the ionic conductivity of Gd-doped CeO 2 increases as the grain size decreases and the ionic conductivity goes through a maximum at about 300-500 nm. In a recent work, Tschope and co-worker showed that about two orders of magnitude lower electrical conductivity compared to microcrystalline material was observed [53].…”