In:
Journal of Applied Crystallography, International Union of Crystallography (IUCr), Vol. 49, No. 3 ( 2016-06-01), p. 997-1008
Abstract:
This article reports a comprehensive investigation of the average and local structure of La 5.6 WO 12−δ , which has excellent mixed proton, electron and oxide ion conduction suitable for device applications. Synchrotron X-ray and neutron powder diffraction show that a cubic fluorite supercell describes the average structure, with highly disordered lanthanum and oxide positions. On average, the tungsten sites are sixfold coordinated and a trace [3.7 (1.3)%] of anti-site disorder is detected. In addition to sharp Bragg reflections, strong diffuse neutron scattering is observed, which hints at short-range order. Plausible local configurations are considered and it is shown that the defect chemistry implies a simple `chemical exchange' interaction that favours ordered WO 6 octahedra. The local model is confirmed by synchrotron X-ray pair distribution function analysis and EXAFS experiments performed at the La K and W L 3 edges. It is shown that ordered domains of ∼3.5 nm are found, implying that mixed conduction in La 5.6 WO 12−δ is associated with a defective glassy-like anion sublattice. The origins of this ground state are proposed to lie in the non-bipartite nature of the face-centred cubic lattice and the pairwise interactions which link the orientation of neighbouring octahedral WO 6 sites. This `function through frustration' could provide a means of designing new mixed conductors.
Type of Medium:
Online Resource
ISSN:
1600-5767
DOI:
10.1107/S1600576716006415
DOI:
10.1107/S1600576716006415/kc5035sup1.cif
Language:
Unknown
Publisher:
International Union of Crystallography (IUCr)
Publication Date:
2016
detail.hit.zdb_id:
2020879-0
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