CERETTI, Monica; WAHYUDI, Olivia; COUSSON, Alain; VILLESUZANNE, Antoine; MEVEN, Martin; PEDERSEN, Bjørn; BASSAT, Jean-Marc.; PAULUS, Werner

doi:10.1039/c5ta05767a

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CERETTI, Monica
Institut Charles Gerhardt Montpellier - Institut de Chimie Moléculaire et des Matériaux de Montpellier [ICGM]

WAHYUDI, Olivia
Institut des Sciences Chimiques de Rennes [ISCR]
Institut de Chimie de la Matière Condensée de Bordeaux [ICMCB]

COUSSON, Alain
Laboratoire Léon Brillouin [LLB - UMR 12]

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Article de revue

Ce document a été publié dans

Journal of Materials Chemistry A. 2015, vol. 3, n° 42, p. 21140-2148

Royal Society of Chemistry

Résumé en anglais

We investigated the structure of Nd2NiO4+δ and Pr2NiO4+δ by single crystal neutron diffraction studies. While the real structure of both compounds is incommensurate, the scattering density of the respective average structures was explored using the Maximum Entropy Method. Unusually high displacement factors were found for the equatorial and apical oxygen atoms showing respectively large displacement amplitudes towards [001] and [110] with respect to the F-symmetry cell. The shifts of the apical oxygen atoms reach up to 1 Å from their average position, corresponding to a 25° tilt of the NiO6 octahedra. At 400 °C, i.e. slightly above the orthorhombic-tetragonal phase transition, the anharmonic apical oxygen displacements towards [110] in the commensurate tetragonal parent structure are strongly enhanced, showing a double-well potential and pointing towards the interstitial vacancy sites, creating a quasi continuous shallow energy diffusion pathway between apical and interstitial oxygen sites. These large displacement amplitudes are considered to be – at least partially – of dynamical origin, which is consistent with a phonon assisted diffusion mechanism, already activated at very moderate temperatures.< Réduire

DOI

http://dx.doi.org/10.1039/c5ta05767a

Project ANR

Mécanismes assistés pour la conduction par ion oxygène dans des oxydes non stœchiométriques - ANR-14-CE05-0016

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Importé de hal

Unités de recherche

Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB) - UMR 5026