Evidence of local defects in the oxygen excess apatite La{sub 9.67}(SiO{sub 4}){sub 6}O{sub 2.5} from high resolution neutron powder diffraction

Journal Article · Tue Dec 15 00:00:00 EST 2009 · Journal of Solid State Chemistry

DOI:https://doi.org/10.1016/j.jssc.2009.09.031· OSTI ID:21372432

Guillot, Stephanie ^[1]; Beaudet-Savignat, Sophie ^[1]; Lambert, Sebastien ^[1]; Vannier, Rose-Noelle; Roussel, Pascal ^[2]; Porcher, Florence ^[3]

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1. CEA Le Ripault, BP 16, 37260 Monts (France)
2. Unite de Catalyse et de Chimie du Solide, Equipe de Chimie du Solide, UMR CNRS 8181, ENSCL-Universite des Sciences et Technologies de Lille, 59652 Villeneuve d'Ascq (France)
3. Laboratoire Leon Brillouin, CEA Saclay, 91191 Gif sur Yvette (France)

From neutron diffraction data collected at 3 K on a powder of La{sub 9.67}(SiO{sub 4}){sub 6}O{sub 2.5} composition and a careful examination of the average structure, a model was proposed to explain the oxygen over-stoichiometry in the apatite structure. This model leads to realistic distances to neighbouring atoms. Moreover, it accounts perfectly for the maximum oxygen content observed in these materials. Up to 0.5 oxygen atom located at the vicinity of the 2a site (0, 0, 1/4) would be shifted to a new interstitial position in the channel at (-0.01, 0.04, 0.06), creating a Frenkel defect, with the possibility of a maximum occupancy in this site equal to twice the Frenkel defect numbers. This structural model is in good agreement with the oxygen diffusion pathways recently proposed by Bechade et al. (2009) using computer modeling techniques. It supports preferred oxygen diffusion pathways via interstitial oxygen atoms and vacant sites along [0 0 1], close to the centre of the La(2)-O channels. - Graphical abstract legend: Structural defect position and possible conduction mechanism along the c-axis (representation of two adjacent unit-cells)

• OSTI ID: 21372432
• Journal Information: Journal of Solid State Chemistry, Vol. 182, Issue 12; Other Information: DOI: 10.1016/j.jssc.2009.09.031; PII: S0022-4596(09)00466-6; Copyright (c) 2009 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0022-4596
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
APATITES
COMPUTERIZED SIMULATION
DIFFUSION
FRENKEL DEFECTS
INTERSTITIALS
LANTHANUM COMPOUNDS
NEUTRON DIFFRACTION
SILICATES
SOLID OXIDE FUEL CELLS
STRUCTURAL MODELS
COHERENT SCATTERING
CRYSTAL DEFECTS
CRYSTAL STRUCTURE
DIFFRACTION
DIRECT ENERGY CONVERTERS
ELECTROCHEMICAL CELLS
FUEL CELLS
HIGH-TEMPERATURE FUEL CELLS
MINERALS
OXYGEN COMPOUNDS
PHOSPHATE MINERALS
POINT DEFECTS
RARE EARTH COMPOUNDS
SCATTERING
SILICON COMPOUNDS
SIMULATION
SOLID ELECTROLYTE FUEL CELLS
VACANCIES