A heavily subtituted manganite in an ordered nanocomposite for long-term energy applications

Abstract

The implementation of nano-engineered composite oxides opens up the way towards the development of a novel class of superior energy materials. Vertically aligned nanocomposites are characterized by a coherent, dense array of vertical interfaces, which allows for the extension of local effects to the whole volume of the material. Here, we use such a unique architecture to fabricate highly electrochemically active nanocomposites of lanthanum strontium manganite and doped ceria with unprecedented stability and straight applicability as functional layers in solid state energy devices. Direct evidence of synergistic local effects for enhancing the electrochemical performance, stemming from the highly ordered phase alternation, is given here for the first time using atom-probe tomography combined with oxygen isotopic exchange. Interface-induced cationic substitution, enabling lattice stabilization, is presented as the origin of the observed long-term stability. These findings reveal a novel route for materials nano-engineering based on the coexistence between local disorder and long-range arrangement.

Visualizing local fast ionic conduction pathways in nanocrystalline lanthanum manganite by isotope exchange-atom probe tomography

“…The region was confined to the edge of the analyzed specimen and it was observed to have high Ga, C, and H concentrations and greater overall background counts in the mass spectrum. The large field of view obtained from these specimens, which was not observed previously, 12,20 is tentatively assigned to the specific film–substrate combination and in particular to the very high evaporation field of the alumina substrate. 24…”

“…(Please note that some uncertainty in the absolute atomic concentration may be introduced by the APT technique). 12,30 Fig. 4a (La contour) also highlights a strong modulation of La concentration (especially in the proximity of the fast oxygen diffusion pathways), which is complementary to Sr ( cf.…”

“…as fuel cell cathodes) is based on MIEC/oxygen conductive uorites (doped ceria or zirconia) composites. [10][11][12] Enhancing the bulk conductivity of MIECs is therefore of primary importance for activating the bulk reaction and oxygen transport path and providing a potentially superior alternative to triple phase boundarybased SoA composites. Recent works have demonstrated a substantial enhancement of surface exchange rate and oxygen diffusivity, with respect to the bulk, for example at grain boundaries (GBs) of La 0.8 Sr 0.2 MnO 3 (LSM), a model interfacedominated MIEC.…”

“…20 In our previous studies, isotope exchange of thin lms under controlled conditions allowed a direct observationand reliable quanticationof fast oxygen diffusion pathways at LSCr grain boundaries and LSM-ceria interfaces. 12,20 Independent work by Kaspar et al recently presented a similar approach for the study of buried Fe 2 O 3 interfaces, conrming the broad relevance of the isotope exchange APT (IE-APT) approach. 23 In the present study, IE-APT was used for the rst-time visualizationand direct quanticationof previously reported enhancement of local oxygen transport in interfacedominated LSM.…”

Influence of Y-substitution on phase composition and proton uptake of self-generated Ba(Ce,Fe)O3−δ–Ba(Fe,Ce)O3−δcomposites

“…The mismatch in the ionic radii of Y 3+ (0.9 Å) and Ce 4+ (0.87 Å) can lead to strain in the Ce-rich phase, although the size effect is more severe for Y in the Fe-rich phase. Intermixing of the cations, including dissolution of part of the Y 3+ in the Fe-rich phase, may be a means to reduce this strain, 38 but leads to a decrease in the proton uptake. Ytterbium was explored as an alternative substituent ion for the Ba(Ce,Fe)O 3Àd series to counteract strain-induced cation intermixing, since Yb 3+ (0.868 Å) has almost the same ionic radius as Ce 4+ .…”